___ it be a mistake?

问题描述:

___ it be a mistake?
a) must
b) may
c) can
d) should

选c,can [那可能是个错误吗?]
情态动词表推测时,疑问句或否定句用can
must用于肯定句,表示“一定,肯定”
may用于肯定句,表示“也许,可能”
should(应该),与题意不符.