问题详情

Each person at a party shook hands exactly once with each of the other people at the party. There was a total of 21 handshakes exchanged at the party.
Column A Column B
The number of people at the party 8
A．if the quantity in Column A is greater
B．if the quantity in Column B is greater
C．if the two quantity are equal
D．if the relationship cannot be determined from the information given请帮忙给出正确答案和分析，谢谢！