The 150 pound people that jumped from the towers as the flames blistered their bodies , made bigger craters than this six ton engine when their chests and brains exploded on the concrete below .

Question with options to choose from: What may be the reason they jumped ?
OPT:
[I] The window collapsed .
[II] The building collapsed .
[III] The engine collapsed .
[IV] The plane collapsed .
[II]