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.
Zhang Heng, one of _____ best-known Chinese astronomers, showed a strong interest in _____ astronomy as a child.
Samuel was _____ why few of his friends attended his birthday party.
_____ life exists on any other planet in the solar system still remains a question.
Later, the naughty boys _____ to the English teacher for having played a trick on her the other day.
The company is deep in _____, so you’d better avoid dealing with it.