He is so skillful that he can draw a picture at an object in      a human hair.

A．one-twentieth the thicker than

B．one-twentieth the thick of

C．one-twentieth the thickness of

D．one-twenty thicker than

一位25岁男子来到门诊，述三个月前下楼梯时左膝扭伤，当时膝部肿胀，疼痛，二周后好转。近日关节不稳，伴疼痛。体检：左股四头肌轻度肌萎缩，内侧关节间隙压痛，回旋挤压试验（±）。X线片未见异常。对确诊最可靠的检查是（）

A.关节穿刺关节液检查

B.超声波检查

C.关节镜检查

D.X线断层

E.ECT检查