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Youmustkeeponworkingintheeveningyouaresureyoucanfinishthetaskintime.[]A.asB.ifC.whenD.unless

题目详情
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
▼优质解答
答案和解析
D