Apersonwhohassleptwellwillhaveaclearmindandworkefficie...

问题详情：

 A person who has slept well will have a clear mind and work efficiently in the daytime

______ people with sleep disorders find it difficult to concentrate during the day.

A. unless             B. while

C. if                 D. until

【回答】

B

知识点：连词

题型：选择题