The best way Tom thought of his strength is to run for 30 minutes every day.A. building up

问题补充：

The best way Tom thought of his strength is to run for 30 minutes every day.

A. building up

B. to build up

C. build up

D. being built up

答案：

A. building up

(答案→)B. to build up

C. build up

D. being built up

解析：考查固定短语。The way to do sth/of doing sth做某事的方法；Tom thought of是定语从句修饰先行词the best way.句意：TOM考虑的最好的增强体力的方法是明天跑30分钟。