Of all the subjects, I like ____ history best because it gives us ____ useful knowledge of things in the past.

A．the; a

B．不填; a

C．a; the

D．a; 不填

成人股骨头无菌坏死病变始于（）

A．滑膜

B．肌肉及肌腱

C．软骨

D．骨

E．关节囊