What must drivers be cautious of when a streetcar has stopped at a pedestrian island?

Answer: C — Watch for passengers getting on and off

When a streetcar has stopped at a pedestrian island, drivers must be particularly attentive to the potential presence of passengers who are getting on and off the streetcar. Passengers may not always be visible or aware of approaching traffic, and they may step into the roadway unexpectedly as they exit or board the vehicle. This situation requires drivers to maintain a heightened level of vigilance to prevent accidents and ensure the safety of all individuals involved, especially those who are crossing or preparing to cross the street. Being aware of this dynamic is critical to safe driving practices around streetcars, especially in areas where pedestrian traffic is expected.