30. How long do you think it will be we can find a new water source?A. afterB. beforeC. w

问题补充：

30. How long do you think it will be we can find a new water source?

A. after

B. before

C. when

D. Since

答案：

A. after

(答案→)B. before

C. when

D. Since

解析：可联系答.案.网客服索取。