I think and the problem could be settled.A. A bit more effortB. So long as you keep up

问题补充：

, I think, and the problem could be settled.

A. A bit more effort

B. So long as you keep up your spirits

C. If you doubt your efforts

D. Making great efforts

答案：

(答案→)A. A bit more effort

B. So long as you keep up your spirits

C. If you doubt your efforts

D. Making great efforts

解析：考查动词形式。本题考查祈使句 + and + 陈述句，题中用省略，故A bit more effort = Make A bit more effort。选A。