恢复缺失牙形态和功能的是（）

A.固位体

B.桥体

C.固定连接体

D.活动连接体

E.小连接体

A cofferdam is（）.

A.any deck below the main deck and above the lowest deck

B.a member that gives fore-and-strength

C.made by placing two bulkhead a few feet apart

D.a heavy fore-and-aft beam under the deck