What is the first behavior a police officer might look for in an impaired driver?

Answer: B — Weaving within the lane

The first behavior a police officer might look for in an impaired driver is weaving within the lane. This behavior is often a crucial indicator of impaired driving because it suggests a lack of control and diminished ability to maintain a steady course. When a driver is under the influence of alcohol or drugs, their reaction times and coordination can be severely affected, leading to swerving or drifting within their lane. This erratic behavior warranted an officer's attention as it typically signifies impairment more strongly than other driving irregularities. While actions like speeding, running stop signs, or driving with headlights off can indicate reckless or distracted driving, they may not directly point to impairment in the way that weaving does. Weaving within the lane clearly demonstrates the driver's struggle to maintain control, which is a classic sign of impairment. Given this context, observing a driver weaving would likely prompt further investigation by law enforcement to assess the driver's condition.