The answer to this is subjective and depends to a great degree on what your textbook and/or your teacher says. I would argue that the best of the answers is D. A is the only other answer that is plausible.
The War Powers Act was meant to help fix the problems that led to the fiasco in Vietnam. It was supposed to take away the President's power to unilaterally go to war. However, this was not something that was really going to heal the wounds of what had already happened.
The opening of the Vietnam Veterans Memorial did much more to heal the wounds. For the first time, Americans of all sorts were able to say "thank you," as it were, to the Vietnam veterans who had gotten such a bad reception when they actually came home from combat. It also allowed Americans to honor them for their sacrifices. This helped to bridge the gap between those who had fought in and/or supported the war and those who had not.