内皮层细胞为凯氏带增厚的植物是（）。A.单子叶植物 B.有次生生长的双子叶植物 C.

电除尘器电极为什么不用直流正压而要用直流负压，说明其原因？

用适当的介词填空。

1. The black shirt is _____ sale for eight dollars.    

2. They have shorts_____ all colors.    

3. What does your father do _____ Fridays?  

4. Mona often goes to see movies_____ her sisters on weekends.  

5. His cousin is good_____her friends.    

6. Her sister usually goes to school_____seven-thirty.    

7. These old people love to listen _____ Mrs Black.    

8. Please write_____me soon.    

9. Does your mother want to know_____my family?    

10. The girl usually plays ping-pong_____two hours after school.

按我国高血压标准规定，凡舒张压持续>90mmHg，不论收缩压如何均列为高血压。

内燃机工作中最常见的摩擦是（）摩擦。

施工单位项目部向建设单位领取施工图，仪表施工队向（）领取施工图。

A、仪表施工负责人

B、设备组

C、项目部

D、材料组