问题
选择题
Only in this way, directed by the teacher, ______work out the problem the day before.
A．had they
B．they could
C．could they
D．did they
答案
答案：D
考查倒装句。当only位于句首是，主句采用部分倒装，助动词提前。句意：只有按照老师指导的这种方法，前一天他们才能解决这个难题。结合语境可知本句描述的是过去的动作，故用一般过去时态。助动词用did，选D。