“x平方的2倍与y的差”用代数式可表示为______．

阅读理解

      Dick and Ellen come from America. Now they are in Tianjin. Every morning they get up very early.

Then they go to work by car. They start their work at 8:30. They are very busy. They have lunch at 12:30. After lunch they work again. They finish their work at 5:30 p.m. In the evening they take Chinese lessons. They want to learn Chinese. They want to talk with Chinese people. They often say "Chinese people are

very friendly". They like to stay in China and they like to work with Chinese people.

1. Where are Dick and Ellen?

A. In America.

B. In Beijing.

C. In Tianjin.

2. Do they get up very late every morning?

A. Yes, they do.

B. No, they don’t.

C. No, they doesn’t.

3. When do they begin to work?

A. 8:00.

B. 8:30.

C. 9:00.

4. What do they do in the evening?

A. Stay at home.

B. Watch TV.

C. Take Chinese lessons.

5. Why do they want to learn Chinese?

A. Because they like Chinese.

B. Because they like China.

C. Because they want to talk with Chinese people.

掉头过程中，应严格控制车速，仔细观察道路前后方情况，确认安全后方可前进或倒车。

中国古代农耕方式演变的趋势是[ ]

A．刀耕火种→石器锄耕→铁犁牛耕

B．石器锄耕→刀耕火种→铁犁牛耕

C．铁犁牛耕→刀耕火种→石器锄耕

D．石器锄耕→铁犁牛耕→刀耕火种

关于小舞蹈病的治疗和预后叙述错误的是（）

A.患者应卧床休息，保持安静，注意保证营养

B.给予青霉素、强的松或水杨酸钠等抗风湿治疗

C.对症处理可应用安定、氯丙嗪、氟哌啶醇、抗癫药等治疗

D.患者舞蹈样动作常在病后2～4周内加重，3～6个月内自行缓解，且无复发

E.适当的治疗可缩短病程

沼气脱硫主要有生物脱硫、化学脱硫两种方法。