螺杆泵振动的原因是什么？

阅读下面短文，并借助上下文和插图补充所缺信息。每个空只能填写一个形式正确、意义相符的单词。

     "Daddy, can I learn to play the (1) _______? I'll try very hard." Sarah asked her (2)_______, Mr White.

     "All right," Mr White said. "I'll (3)_______ for you to have lessons for six weeks. If you play well, you

can go on with your lessons. If you don't, I will (4)_______ the lessons."

     "OK, Daddy," Sarah said.

     Mr White found her a good and expensive (5)_______ and Sarah began her lessons.

     Six weeks later, Sarah said to Mr White, "I'm (6)_______ to play for you, Daddy."

     "Fine, Sarah," Mr White said."Begin."

    She began to play. She didn't play well. She made a terrible noise.

     Her father had one of his friends with him. The friend put his hands over his (7)_______ when he heard

the noise.    

    When Sarah (8)_______, her father said,"Well done, Sarah. You can go on with your lessons."

    Sarah ran happily out of the room. Mr White's friend turned to him."You've spent a lot of (9)_______,

but she still plays very (10)_______," he said.

     Mr White said, "Since she started learning the piano, I've been able to buy five apartments (单元房间) in

this building very cheaply. In another six weeks, I'll own the whole building."

一摄影爱好者拍到了一张雨天后的照片，照片中一人站在屋檐下，屋檐向下滴水，可以清楚地看到一滴水正好要滴下，一滴水刚好落地．中间还有两滴水，较低的一滴水正好在照片中人的肩等高的位置，此人身高约1.8m，每滴水的形成时间近似相同．则屋檐高最接近（　　）

A．1.5m

B．2.2m

C．2.7m

D．3.5m

关于革兰阴性菌细胞壁的叙述，哪一项是错误的（）。

A.肽聚糖含量少

B.缺乏五肽桥

C.致病力与所含脂多糖有关

D.对溶菌酶较敏感

E.有蛋白糖脂外膜

下颌第三磨牙阻生适宜做龈瓣切除术的情况是（）

A.水平阻生，冠周炎反复发作

B.垂直阻生，升支前方有足够空隙，对颌牙位置正常

C.前倾阻生，前方邻牙远中龋坏

D.前倾阻生，龈瓣上有咬痕

E.颊向阻生，对颌牙位置正常

谈认识，主要是考察学生对词汇规范是否持正确的态度。