问题补充:
24. You ought to have put the milk in the refrigerator, and now sour.
A. it smell
B. it is smelt
C. it smells
D. it is smelling
答案:
A. it smell
B. it is smelt
(答案→)C. it smells
D. it is smelling
解析:考查时态。句意:你应该已经把牛奶放进冰箱了,可是现在闻起来酸了吧!结合语境可知下文描述的是现在客观存在的状态,故用一般现在时态,选C。