摘要： 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 答案 D 解析 unless引导一个状语从句.意思同if...not...如误选C.是因为没有正确理解句子的意思.句意为:你必须在晚上继续工作.除非你确信会按时完成任务.

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