---Tom studies hard.Mary studies even harder.Jack hardly studies.Of the three, who studies the hardest? ---___ studies the hardest.

A．Tom

B．Mary

C．Jack

D．Nobody

早期股骨头缺血性坏死的首选检查方法为（）

A.CT平扫

B.CT增强

C.CT平扫+增强

D.MRI

E.X线平片