What is the recommended action to check your blind spot before changing lanes to the left?

Answer: D — Glance over your left shoulder

When changing lanes to the left, the recommended action is to glance over your left shoulder. This maneuver allows you to directly check the area in your blind spot on the left side of your vehicle. The blind spot is the area that may not be visible through your mirrors, and turning your head enables you to see if there are any vehicles or obstacles that you may not have detected otherwise. Using your left shoulder instead of relying solely on mirrors provides a comprehensive view of the lane you're about to enter. While mirrors are helpful for monitoring traffic behind and alongside your vehicle, they cannot replace the visual confirmation that comes from physically turning your head. This is important to ensure safety and prevent collisions when you change lanes.