Bill was doing a lot of physical exercises to build up his .A. abilityB. forceC. strengthD

问题补充：

Bill was doing a lot of physical exercises to build up his .

A. ability

B. force

C. strength

D. mind

答案：

A. ability

B. force

(答案→)C. strength

D. mind

解析：选择C。根据句意，Bill做大量的体育锻炼就是为了强健体魄。与“强健体魄”有关的就是strength, force也有“力量”的意思，不过一般指“外力”，“强制性力量”。