问题补充：
His mother asked him watch TV he finished his homework.
A. not to , when
B. to, untill
C. to not. Till
D. not to; until
答案：
A. not to , when
B. to, untill
C. to not. Till
(答案→)D. not to; until
解析：ask sb (not) to do sth.意思是：叫某人（不）要做某事；not…until…直到….才.
