【题目】After three days' waiting, there was a little doubt in the mother's mind _______ the police could find her lost child.
A. howB. that
C. whereD. whether
在线课程【答案】D
【解析】
考查同位语从句。句意为：在等了三天之后，母亲的心中产生了点怀疑，警察是否能够找到她丢失的孩子。whether the police could find her lost child是同位语从句，是对doubt起着补充说明作用。故选D。