问题
选择题
They must have finished the work by the end of last month, ______?
A．hadn’t they
B．mustn’t they
C．haven’t they
D．didn’t they
答案
答案：A
题目分析：句意：他们上个月的月底一定已经完成了这项工作，不是吗？当情态动词must表推测时，其反义疑问句要根据实际情况来判断，本题的时间状语是by the end of last month,应与过去完成时连用，还原一下本题应为：They had finished the work by the end of last month.故选C。