已知集合A={-1,1},B={x|mx=1},且B⊆A,则m的值为( )
A.1或-1或0 B.-1
C.1或-1 D.0
A 因为B⊆A,所以B=∅或{1}或{-1},即m=0或=1或=-1,得到m的值为1或-1或0.