What must vehicle 1 do before turning left?

Answer: B — Yield to vehicle 3

Before turning left, vehicle 1 must yield to vehicle 3 in order to safely execute the turn. When turning left at an intersection, it is crucial for the vehicle making the turn to assess oncoming traffic and any vehicles that may be approaching from the opposite direction. Yielding to other vehicles ensures that vehicle 1 does not collide with vehicle 3, allowing for a smooth and safe transition through the intersection. While driving straight through the intersection or stopping at a stop sign may seem relevant in different contexts, they do not directly pertain to the requirement of yielding to other vehicles during a left turn. Asking for directions from other drivers is also irrelevant to the actions needed when preparing to make a turn. The focus on yielding reinforces the importance of being aware of other traffic as a key aspect of safe driving practices.