题目

It is drier in Shenyang than ________.And we have _____rain this spring .The trees and grass don’t grow well. A．it in Guangzhou ,a little                              B．that in Guangzhou, little C．in Guanzhou, little                                  D．in Guanzhou , a little 答案：C9．设集合A={-1，1}，集合B={x|ax=1，a∈R}，则使得B⊆A的a的所有取值构成的集合是（　　）A．{0，1}B．{0，-1}C．{1，-1}D．{-1，0，1}