Before changing lanes, what is the first step a driver should take?

Answer: B — Check mirrors and look over the shoulder.

The first step a driver should take before changing lanes is to check mirrors and look over the shoulder. This action is crucial for ensuring that the driver is aware of their surroundings, particularly any vehicles or obstacles that may be in the blind spots. Checking mirrors helps the driver identify what is directly behind and beside them, while looking over the shoulder provides additional visual confirmation that the lane change can be completed safely. This process significantly reduces the risk of collisions and ensures the driver is making an informed decision based on the current traffic conditions. Using the turn signal immediately, while important for signaling intentions to other drivers, should come after confirming that the lane change is safe to perform. Accelerating to gain speed is not advisable unless necessary for merging into traffic; it can create dangerous situations when changing lanes. Lastly, waiting for a clear path ahead is part of the decision-making process but is not the immediate first step that includes assessing the current situation around the vehicle. Thus, the most logical first action is to check mirrors and look over the shoulder.