The children are seldom encouraged up late at night preparing their lessons,if .
A. staying;once
B. to stay;ever
C. staying;sometimes
D. to stay;never
网友回答
A. staying;once
(答案→)B. to stay;ever
C. staying;sometimes
D. to stay;never
解析：encourage sb. to do sth. 鼓励某人做某事；if ever 如果有。