Missouri: Alcohol and drugs — Part 4 Practice Test
Questions in this part include: “At what BAC is it illegal for an adult driver who is 21 or older and not driving a commercial vehicle to drive?” · “What kind of drug should you not take before driving?”
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Questions are original and based on the official manual "Missouri Driver Guide" (Revised August 2026), Missouri Department of Revenue.
All 19 questions in this practice test
Take the test above first, then use this list to study. Tap “Show answer” to see the correct answer and explanation.
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At what BAC is it illegal for an adult driver who is 21 or older and not driving a commercial vehicle to drive?
- 0.08% or more
- 0.05% or more
- 0.10% or more
- 0.15% or more
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Correct answer: 0.08% or more
It is illegal to drive with a blood alcohol content of 0.08% or more.
Source: Missouri Driver Guide (Revised August 2026), page 71 · Open this page in the manual (Manual page 71)
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At what BAC is it illegal for a commercial vehicle driver to drive?
- 0.05%
- 0.06%
- 0.04%
- 0.10%
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Correct answer: 0.04%
The guide gives 0.04% as the illegal BAC for commercial vehicle drivers.
Source: Missouri Driver Guide (Revised August 2026), page 71 · Open this page in the manual (Manual page 71)
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What BAC applies to a driver who is under 21 years of age?
- 0.05%
- 0.02%
- 0.06%
- 0.10%
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Correct answer: 0.02%
The guide gives 0.02% as the BAC limit for drivers under 21.
Source: Missouri Driver Guide (Revised August 2026), page 71 · Open this page in the manual (Manual page 71)
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Under what age is it illegal to possess or purchase alcohol?
- 16
- 18
- 19
- 21
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Correct answer: 21
It is illegal to possess or purchase alcohol if you are under the age of 21.
Source: Missouri Driver Guide (Revised August 2026), page 71 · Open this page in the manual (Manual page 71)
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According to the guide, how many drinks could in many cases place you over the legal blood alcohol limit?
- Four
- Two
- Six
- Eight
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Correct answer: Two
Even one drink is likely to affect your ability to drive safely and in many cases two drinks could place you over the legal blood alcohol limit.
Source: Missouri Driver Guide (Revised August 2026), page 71 · Open this page in the manual (Manual page 71)
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Which statement about medications and driving is correct?
- Medications taken as directed never impair driving
- Only illegal drugs can impair driving
- Over-the-counter medicines never impair driving
- Even medicine taken as directed can impair your driving
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Correct answer: Even medicine taken as directed can impair your driving
All medications, both prescription and over-the-counter, are potentially dangerous and can impair driving, even when taken as directed.
Source: Missouri Driver Guide (Revised August 2026), page 71 · Open this page in the manual (Manual page 71)
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If you are not sure whether a medication will affect your driving, whom does the guide say to check with?
- Your physician or pharmacist
- Your insurance company agent
- A license office employee
- A police officer on duty
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Correct answer: Your physician or pharmacist
The guide says to check with your physician or pharmacist and read the warning label.
Source: Missouri Driver Guide (Revised August 2026), page 71 · Open this page in the manual (Manual page 71)
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What effect can over-the-counter medicines for colds and allergies have on you?
- They can make you more alert for several hours
- They can improve your night vision
- They can make you drowsy
- They have no effect on driving ability
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Correct answer: They can make you drowsy
Over-the-counter medicines for colds and allergies can make you drowsy and affect your driving ability.
Source: Missouri Driver Guide (Revised August 2026), page 71 · Open this page in the manual (Manual page 71)
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What can pep pills, “uppers,” and diet pills cause later, after making a driver more alert for a short time?
- Nervousness, dizziness, and poor concentration
- Longer-lasting alertness and better focus
- Sharper vision at night and better focus
- Faster reaction time and steadier hands
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Correct answer: Nervousness, dizziness, and poor concentration
After the short period of alertness, these pills can cause a person to be nervous, dizzy, and not able to concentrate.
Source: Missouri Driver Guide (Revised August 2026), page 71 · Open this page in the manual (Manual page 71)
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What kind of drug should you not take before driving?
- Any drug that comes in a liquid form
- Any drug you have taken at least once before
- Any drug that “may cause drowsiness or dizziness”
- Any drug that is sold without a prescription
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Correct answer: Any drug that “may cause drowsiness or dizziness”
Any drug that “may cause drowsiness or dizziness” is one you should not take before driving.
Source: Missouri Driver Guide (Revised August 2026), page 71 · Open this page in the manual (Manual page 71)
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What does the guide say about taking medications prescribed for someone else?
- It is safe if the dose is small
- It is dangerous and illegal
- It is legal if you have the same illness
- It is allowed if you do not drive afterward
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Correct answer: It is dangerous and illegal
The guide says not to take medications prescribed for someone else because it is dangerous and illegal.
Source: Missouri Driver Guide (Revised August 2026), page 71 · Open this page in the manual (Manual page 71)
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What does the guide advise about mixing alcohol with your medications?
- It is safe with over-the-counter medicines only
- It is safe if you drink only a small amount
- It is safe if you wait one hour before driving
- Do not mix them, prescribed or over the counter
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Correct answer: Do not mix them, prescribed or over the counter
The guide says not to mix alcohol with medications, whether prescribed or over the counter.
Source: Missouri Driver Guide (Revised August 2026), page 71 · Open this page in the manual (Manual page 71)
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According to the guide, when is it legal and safe to drive while under the influence of marijuana, even though medical marijuana was approved by Missouri voters?
- When the marijuana was prescribed
- Never
- When it is used in small amounts
- When you drive only short distances
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Correct answer: Never
The guide says it is never legal or safe to drive while under the influence of marijuana.
Source: Missouri Driver Guide (Revised August 2026), page 72 · Open this page in the manual (Manual page 72)
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Which effect of marijuana on drivers does the guide list?
- It can sharpen your judgment of distance
- It can shorten your reaction time a lot
- It can improve your coordination slightly
- It can impair judgment of time and distance
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Correct answer: It can impair judgment of time and distance
Marijuana can impair cognitive function, impair judgment of time and distance, and decrease coordination.
Source: Missouri Driver Guide (Revised August 2026), page 72 · Open this page in the manual (Manual page 72)
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What happened when drivers used alcohol together with marijuana in the research studies the guide describes?
- They were even more impaired, with even more lane weaving
- They were less impaired than with marijuana alone
- They showed no change in lane weaving
- They showed faster reaction times
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Correct answer: They were even more impaired, with even more lane weaving
Research found that the use of alcohol with marijuana made drivers even more impaired, causing even more lane weaving.
Source: Missouri Driver Guide (Revised August 2026), page 72 · Open this page in the manual (Manual page 72)
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Which is one of the greatest predictors of someone developing an addiction?
- Late use
- Using only prescribed medication
- Early use
- Working long hours
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Correct answer: Early use
One of the greatest predictors of someone developing an addiction is early use.
Source: Missouri Driver Guide (Revised August 2026), page 72 · Open this page in the manual (Manual page 72)
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Why is a young person more susceptible to developing a substance use disorder?
- A young brain can be damaged quicker and more severely
- Young people have slower reflexes than most adults
- Young people drink larger amounts than adults do
- Young people are less likely to seek treatment later
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Correct answer: A young brain can be damaged quicker and more severely
A young person’s under-developed brain can become damaged quicker and more severely than an adult brain using the same substances.
Source: Missouri Driver Guide (Revised August 2026), page 72 · Open this page in the manual (Manual page 72)
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What does the guide advise if you are going to drink?
- Drive only on roads that you know very well
- Drive slowly and stay in the right-hand lane
- Let someone else drive who has not been drinking
- Wait ten minutes after your last drink and drive
Show answer
Correct answer: Let someone else drive who has not been drinking
The guide advises that if you are going to drink, you let someone else drive who has not been drinking.
Source: Missouri Driver Guide (Revised August 2026), page 67 · Open this page in the manual (Manual page 67)
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How much alcohol may affect your driving ability?
- Only more than two drinks
- Even a small amount
- Only more than four drinks
- Only an amount over the legal limit
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Correct answer: Even a small amount
Even a small amount of alcohol may affect your driving ability.
Source: Missouri Driver Guide (Revised August 2026), page 67 · Open this page in the manual (Manual page 67)