Why did suspicion focus on osama bin laden after the september 11 terrorist attacks?
a) witnesses had seen and identified him at the world trade center on the morning of the attacks.
b) he had recently sent a videotape threatening an attack on american soil to u. s. media outlets.
c) the federal aviation authority had caught him on videotape at logan international airport in boston.
d) his terrorist network had announced their intention to kill americans, and it was linked to previous bombings abroad.