The answer is A.
So, like, basically what he did was this: he, like several other south Vietnamese, was tired of the Vietnam War. So he decided to do this thing called "self-immolation", a fancy term for "setting yourself on fire", but for religious reasons. He went to downtown Saigon, settled himself on the corner of a busy intersection, which happened to be adjacent to a government building, prayed, and then doused himself with gasoline and lit himself up. Reports say that he was calm and looked at peace, even while the flames were consuming him. When the flames burnt out, only his heart remained intact. That heart was considered a symbolic symbol to the Buddhist community at the time.
