RNA聚合酶在分类时属于六大酶类中的哪一种：（）A.合成酶类 B.转移酶类 C.裂解

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Tom: Hi, Sally, what do you often do on week-ends?

Sally: I often get up at half past seven, and I often go to the park with my mom at eight thirty.

Tom: When do you do your homework?

Sally: I often do it at one o'clock in the afternoon, and I often go swimming after four o'clock.

Tom: I like swimming, too. Do you like watching TV?

Sally: Yeah. I often watch TV at six o'clock. It's cartoon time.

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( )( )

一般来说，同一个体内牙根最长的是哪一组牙（）

A．上颌尖牙 

B．上颌双尖牙 

C．上颌磨牙 

D．下颌双尖牙 

E．下颌磨牙

无线电波中频率最高的部分是（）

A．紫外线 

B．红外线 

C．高频电磁场 

D．无线电波 

E．微波

正常运行下，污泥房电机启动方式？

为什么要把烧结型半导体陶瓷湿敏元件短时间加热到500摄氏度的高温？