Bill was doing a lot of physical exercise to build up his .A. ability B. force C. strength

问题补充：

Bill was doing a lot of physical exercise 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：名词辨析。A能力；B武力，暴力；C力气；D思维；句意：为了增强体力Bill进行了大量的锻炼。