If 12 boys meet at a reunion and each boy shakes hands exactly once with each of the others, then what is the total number of handshakes	Choices.
A) 41
B) 42
C) 43
D) 66
E) 45

Rationale: "n ( n - 1 ) / 2 = 12 * 11 / 2 = 66 answer : d"
Answer: D