HISTORY HOMEWORK!! please help me... thanks u [ITS MULTIPLE CHOICE]?

a,d,?,b.... ddt was a pesticide that was used to prevent bugs from eating crops, it was found to kill birds and alot of beneficial insects,during the cold war, russians put missle silos carrying nuclear warheads in cuba, 60 miles from florida, it was really scary during that time ( I was a kid then) the watergate conspiracy was when President Nixon and his campaine people wiretapped the dmc, when it was found out, he resigned from being president