In which of the following years will a census be done in the United States

A．an object had exploded three miles above the forest
B．the explosion was not caused by a comet
C．an atomic explosion once happened above the ground
D．some form of life from other planets once visited the earth then

A．the "explosion" caused a loud sound and a big fire
B．the "explosion" caused much damage to the forest
C．scientists didn't explore that area right after the explosion
D．people can't make out the cause of the explosion