C. To show that duck and cover would protect a person during a bomb attack.
That answer doesn't make much sense to us now, but at the time of the 1951 Duck and Cover film released by the US Civil Defense office, that was the message the government was conveying to the American people.
If you look at the other options in the answer choices, all of them (A,B,D) are essentially saying the same thing -- that this was a method that would not work. So the only unique answer in the set -- which was the message from Civil Defense -- was that "duck and cover" was a helpful strategy in the event of a nuclear attack. Truthfully, it would not have been.
