一般而言，经纪人是以( )为主要资源为客户服务的。A．房地产 B．资金 C．设备

There is strong evidence that the          of a father increases the probability that a youngster will use

drugs and engage in criminal activity.    [ ]

A. absence  

B. disappearance  

C. attention

D. concern

QTc的计算公式为（）。

A.

B.

C.

D.

E.

. Now everyone is concerned about how to conquer the economic crisis _______ is very important for us to be able to preserve our standard of living.

A．which success

B．its success

C．the success of which

D．the success of it

根部牙本质的形成取决于（）

A.成釉器

B.牙 * *

C.牙囊

D.上皮根鞘

E.上皮隔

全球划分为多少个时区，每个时区包含经度多少度：（）.

（A）12个，30°

（B）24个，15°

（C）18个，20°

（D）36个，10°