What must you do before changing lanes?

Before changing lanes, it is essential to check mirrors and blind spots, as well as signal your intention to other drivers. This practice ensures that you are aware of any vehicles or obstacles that may be in your path, which is critical for safety. Checking mirrors allows you to see surrounding traffic, while looking into blind spots ensures that there are no vehicles you may not have fully visible. Signaling your intention is equally important, as it informs other road users of your actions, thus helping to prevent accidents.

The other options do not adequately address the necessary safety measures for a lane change. Accelerating quickly can lead to unsafe situations, particularly if other vehicles are close by. Turning off the radio may help with concentration, but it does not replace the need for situational awareness that comes from checking mirrors and blind spots. Reducing speed significantly might be unnecessary and could lead to confusion among other drivers trying to maintain consistent traffic flow.