What sign indicates a driver may be impaired?

Answer: B — Erratic movements and failed sobriety tests

The correct choice highlights the behaviors and indicators associated with impaired driving. When a driver exhibits erratic movements and fails sobriety tests, it is often a clear indication that they may be under the influence of alcohol or drugs. Erratic movements can include swerving, abrupt lane changes, or unusual speed variations, all of which are behaviors that suggest a lack of control or impaired judgment. Sobriety tests are specifically designed to assess a driver's ability to operate a vehicle safely. Failure to pass these tests typically indicates that the driver may have impairments affecting their ability to drive, reinforcing the link between those behavioral signs and potential impairment. In contrast, adhering to traffic signals, driving within speed limits, and making frequent stops are all indicators of responsible driving behavior. These actions typically do not suggest impairment; instead, they often demonstrate a driver who is following the rules of the road and driving safely.