When Apple's Famous 1984 "Big Brother" Ad Aired During the Super

When Apple's famous 1984 "Big Brother" ad aired during the Super Bowl, it reached an estimated 500 million viewers. It aired only once on commercial television, but was seen in later years in at least ten television programs recalling great commercials. For its target audience, the frequency of this ad is measured as

A) one.
B) ten.
C) 500 million.
D) one / tenth.
E) 5 billion (ten times 500 million) .