Final answer:
A motorist with a BAC of 0.10% has a significantly increased risk of causing a motor vehicle accident due to the impairment of critical driving functions by alcohol.
Step-by-step explanation:
If a motorist has reached a Blood Alcohol Concentration (BAC) of 0.10%, the risk of causing a motor vehicle accident significantly increases. Studies have shown that at this level of intoxication, a driver is many times more likely to be involved in a crash compared to a sober driver. Alcohol impairs various cognitive and motor functions critical for safe driving, including judgment, concentration, coordination, and reaction time. This is why there are strict laws against driving under the influence of alcohol.