What should you check when changing lanes to ensure safety?

Answer: C — Blind spots by looking over your shoulder

When changing lanes, it is essential to check blind spots by looking over your shoulder. This action helps drivers be aware of any vehicles or obstacles that may not be visible in their mirrors. Mirrors can provide a good view of surrounding traffic, but they do not capture everything, particularly the areas directly beside and behind the vehicle that may not be covered by the mirror's field of view. Checking blind spots ensures that a driver has a complete understanding of the situation around them before making a lane change, thereby reducing the risk of accidents. This step is crucial as other vehicles, cyclists, or pedestrians may be present in those areas without the driver realizing it when only relying on mirrors. While checking mirrors, the lane in front of you, and being aware of the vehicle's speed are important aspects of safe driving, they do not replace the necessity of checking blind spots, which are a critical component of a comprehensive lane change check.