[单选题]In the long history of humanity, everyone may have to shake hands with other people. If someone makes an odd number of handshakes in his life, he is called a Class A person, otherwise he is called a Class B person. The number of people of type A since ancient times is: (assuming that humans can only shake hands with humans)D57答案窝(daanwo.com)-大学生作业答案及考资分享平台
D57答案窝(daanwo.com)-大学生作业答案及考资分享平台
在人类的历史长河中，每个人都可能要与其他人握手。如果某人在他的一生中进行握手的次数为奇数，则称他为A类人，否则称为B类人。试问从古至今A类人的个数是：(假设人类只能和人类握手)D57答案窝(daanwo.com)-大学生作业答案及考资分享平台
AEven number偶数D57答案窝(daanwo.com)-大学生作业答案及考资分享平台
BOdd number奇数D57答案窝(daanwo.com)-大学生作业答案及考资分享平台
CPrime number 素数D57答案窝(daanwo.com)-大学生作业答案及考资分享平台
DComplete square number 完全平方数