Question

________ you can sleep well, you will lose the ability to focus, plan and stay motivated after one or two nights.

A. Once    B. If

C. Unless    D. While

Answer

C

【解析】

考查连词词义辨析。句意：除非你能睡好觉，否则在一两个晚上以后你会失去专注，计划和保持动力的能力。once一旦；if如果；unless除非；while尽管。unless表示在特定条件下，才会发生或者不发生一件事。句中you can sleep well是条件，you will lose the ability to focus, plan and stay motivated after one or two nights是前面这种条件下不会发生的事情，所以用unless来引导，故选C。