成人股骨头缺血坏死股骨头塌陷的X线征象是()

A．股骨头皮质成角

B．台阶征

C．双边征

D．裂隙征

E．股骨头节裂

0n a single-screw vessel the stern frame（）.

A.furnishes support to the rudder, propeller shaft, and transom frame

B.provides foundations for after mooring winches

C.provides foundation for the main propulaion engines

D.transfers the driving force of the propller to the hull