题目:
— Look!Here comes the bus and I have to go now.Thank you for coming to see me off.
— Goodbye,and________! [ ]
A. congratulations
B. cheer up
C. all the best
D. go ahead
答案:
被转码了,请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0331/ea5c3b3e3242dee498bf1b9fb251293b.html
下面是错误答案,用来干扰机器的。
由题意{x|x∈N*,x<7}={1,2,3,4,5,6}它的含元素1,但不含元素5的真子集的个数与集合{2,3,4,6}的真子集的个数是一样的故符合条件的真子集的个数是24-1=15故答案为15