— ________ he ________ anything about this historic site?

— Yes. That’s why he suddenly becomes so obsessed with it.

A．Has; read

B．Does; read

C．Did; read

D．Had; read

关于支点线的定义，正确的是（）

A.牙之间的连线

B.卡环之间的连线

C.固位体之间的连线

D.支托之间的连线

E.两个主要基牙上直接固位体支托的连线