Final answer:
The true statement about changing lanes is that you should look over your right shoulder when changing to the right lane and your left shoulder when changing to the left lane, to check for blind spots.
Step-by-step explanation:
The statement that is true about changing lanes is A. Look over your right shoulder for a right lane change and your left shoulder for a left lane change. This is because there can be areas that your mirrors do not cover, commonly known as 'blind spots.' Looking over the appropriate shoulder helps you to double-check these blind spots before changing lanes. Statement B is incorrect because even vehicles with two outside mirrors do have blind spots. Statement C is incorrect because you need to look over both shoulders for lane changes to the right and left accordingly, not just over your right shoulder.