卡环是可摘局部义齿的 A．直接固位体 B．间接固位体 C．冠内固位体 D．根外固位体

视网膜上视锥细胞最集中的区域是（）。

A.锯齿缘

B.黄斑区

C.视网膜周边部

D.视 * *

E.视 * * 周围

Many students are ________ chatting online, which wastes them plenty of time.

A．crazy about

B．connected with

C．worried about

D．anxious about

He _______ reading books, but he doesn't_________reading one now.[ ]

A. would  like; like                    

B.  likes; feel  like

C. likes; would like                      

D. would  like; feel  like

通常酶的固定化方法有（）法、（）法，法、（）法。

区域可供水量如何计算？需要什么资料？