关节是骨与骨之间相连接的部位，那么关节的基本结构包括  [ ]

A．关节头、关节窝和关节囊    

B．关节面、关节囊、关节腔  

C．关节头、关节窝、关节面    

D．关节囊、关节腔和关节软骨

0ne function of a hulwark is to（）.

A.help keep the deck dry

B.prevent stress concentrations on the stringer plate

C.protect against twisting forces exerted on the frame of the vessel

D.reinfo ce th eside stringers