gwd1-10

jamesyl327

A set of numbers has the property that for any number t in the set, t + 2 is in the set.  If –1 is in the set, which of the following must also be in the set?

I.    -3
II.    1
III.    5
A.    I only
B.    II only
C.    I and II only
D.    II and III only
E.    I, II, and III

答案是不是错了啊

robinyue

答案好像是D吧? -1在,1就在,3就在,5就在... 但-3不一定在啊..不能反推

SMARTCATHYT

为什么不能反推呢？