The police still haven’t found the lost child but they’re doing all they.A. canB. mayC. m

问题补充：

The police still haven’t found the lost child, but they’re doing all they.

A. can

B. may

C. must

D. should

答案：

(答案→)A. can

B. may

C. must

D. should

解析：本题考查情态动词。can表能力。do all（that）one can意为：“竭尽全力”。句意为：“虽然警察仍未找到那个失踪的孩子，但他们正竭尽所能。”