题目内容：

She was so terribly ill that she had to ask for ________________.
A.a three day leave B.three-days sick leaves
C.a sick leave of three days D.three-day sick leaves

优质解答

A.three 和 day 一起时,除非加连词符,否则是不会出现名词用单数形式的情况的.
B.量词和名词由连词符连接作定语时,一定是单数形式,且病假无论几天都是一次病假,所以就是 a three-day sick leave
D.参见 B
她病得很严重,不得不请了三天病假