给下面多音字注音并组词。

①背（     ）________

　　（     ）________

②更（     ）________

　　（     ）________

③觉（     ）________

　　（     ）________

④勾（     ）________

　　（     ）________

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