, I think, and the problems would be settled.
A. If you double your efforts
B. Making more efforts
C. So long as you don’t lose heart
D. A bit more effort
网友回答
A. If you double your efforts
B. Making more efforts
C. So long as you don’t lose heart
(答案→)D. A bit more effort
解析：根据句中的连词and可知此空缺少祈使句，如果没有and则A、C两个选项都正确。句意：我认为努力些问题就会解决。