问题补充：
― Why you stay in the countryside, where it is not convenient to go shopping?
―But I’ve found it rather valuable for my health.
A. can
B. must
C. may
D. shall
答案：
A. can
(答案→)B. must
C. may
D. shall
解析：本题考查情态动词。选B。问句句意：你为什么非要留在乡下？那里购物非常不便。must在此表示“偏偏，硬要”之意。
