Youmustkeeponworkingintheevening

问题详情：

You must keep on working in the evening________you are sure you can finish the task in time.

A．as                                                      B．if

C．when                                                 D．unless

【回答】

D　本题考查连词的用法。unless意为“除非……(否则)”，引导状语从句。根据句意可知应选D项。

知识点：连词

题型：选择题