— Are you going to Beijing by air?
— It’s fast, but expensive. So I’m not sure. I take a train.
A. may
B. will
C. must
D. should
网友回答
(答案→)A. may
B. will
C. must
D. should
解析：考查情态动词用法。may表示一种可能性比较小的推测，will 将，must是肯定性的推测，should应该，根据题中So I’m not sure，可知是一种不太肯定的推测，所以选A。