How should you check an area beside your vehicle that the mirrors do not show?
Correct answer: C – Look over the appropriate shoulder
Blind spots are areas beside and slightly behind a vehicle that may not appear in the mirrors. Before changing lanes, use the rearview and side mirrors and then look over the appropriate shoulder. Make the lane change only after this check confirms that the neighboring lane is clear.
Source: Nevada Driver’s Handbook — Ch. 3, “Lane Changes”

