—Can we ski on this mountain?
—Of course.However, at no time you do so alone.
A. could
B. might
C. need
D. must
网友回答
A. could
B. might
C. need
(答案→)D. must
解析:at no time意思是“从不,决不”,位于句首时句子用部分倒装,本题情态动词must提到了主语的前面。must与at no time(=not/never)连用的意思是“绝对不行,绝对不允许”。句子意思是“然而,你绝对不能单独在山上滑雪”。