How can you tell that a driver is about to turn?

Answer: B — Their turn signals will be activated

The best indication that a driver is about to turn is when their turn signals are activated. Turn signals are a critical part of safe driving and are specifically designed to communicate a driver's intentions to others on the road. When a driver activates their turn signals, it alerts nearby drivers and pedestrians that they plan to make a turn, allowing everyone to adjust their actions accordingly. This use of turn signals is not only a matter of safety but is also mandated by traffic laws in many jurisdictions, including Arizona. While slowing down abruptly or changing lane positions could suggest that a driver is preparing to turn, these behaviors are less reliable indicators of intention. Looking in the rearview mirror can be part of general driving responsibilities but does not provide a clear signal of an immediate turn. Therefore, the activation of turn signals is the most straightforward and reliable cue that a driver intends to change direction.