Which of the following should be asked regarding medication use history?

The focus of the question is on medication use history, which is a critical aspect of ensuring that commercial drivers are fit for duty. In this context, asking whether the driver is experiencing side effects such as dizziness directly addresses potential risks related to medication use. Side effects can significantly impair a driver's ability to operate a vehicle safely, making it essential to identify any adverse reactions to medications that might compromise their alertness, judgment, or motor skills.

Inquiring about side effects allows for a proactive approach to safety by identifying drivers who may need further evaluation or intervention. This practice aligns with FMCSA guidelines, which emphasize the importance of understanding the medical history and medication use of commercial drivers to prevent accidents caused by impaired driving.

The other options, while relevant in different contexts, do not specifically relate to medication use. Clothing choices, driving at night, and vehicle condition are important factors for a driver’s overall safety and operational readiness, but they do not directly assess how medications might affect the driver's current state or ability to drive safely. Hence, option B stands out as the most relevant question regarding medication use history.