To keep fit, Professor Li _____ cycling as a regular form of exercise. [ ]

A. took up

B. caught on

C. carried out

D. made up

关于空压机转向的表述，不正确的是（）

A.转向不能相反，否则空压机的吸排将相反

B.转向不能相反，否则兼作风扇的飞轮，将改变风向

C.转向不能相反，否则对于强力润滑系统，油泵供油将相反，从而造成严重机损