可摘局部义齿中起辅助固位和增强稳定作用的部分是（）

A.卡环

B.连接体

C.基牙

D.间接固位体

E.人工牙

Was it at the Olympic Games ______ were held this year ______ Liu Xiang got a metal?

A．which; that

B．which; which

C．that; when

D．when; that