简述碾压混凝土施工碾压步骤？

（1）小球带何种电荷；

（2）小球从O点抛出到落回x轴的过程中电势能的改变量;

（3）小球上升的最大高度及初速度v₀;

（4）若要使小球通过P点后作直线运动，则在x轴下方所加匀强电场E₂的最小值及方向。

下列语句中划线的成语使用有误的一项是

A．在这个喧嚣浮躁的世界上，芸芸众生都在为生活忙碌奔波，很少有人能“停下脚步来等等自己的灵魂”。

B．为迎接学校首届文化艺术节，建明和他的搭档们逢场作戏，精心编排了一出反映校园生活的话剧。

C．他是一个技术成熟、经验丰富的选手，这次在奥运会上夺冠，应该是十拿九稳的事。

D．从燕子呢喃到荷花盛开，从鸣蝉噤声荐到大地沉寂，大自然年年如是，周而复始，生生不息。

阅读理解。

     For most students in universities, 20,000 yuan is a big sum. But Xiao Wang paid the money soon after

she learned that she could change to the popular Economics Department.

     But by paying 20,000 yuan with the help of her parents, Xiao Wang can study the economics major she

prefers. "It is difficult for graduates (毕业生) in chemistry to find a good job in recent years," she said. Xiao

Wang is only one of the many freshmen that pay to change to popular majors. Many universities throughout

China offer similar services. The charge for changing majors are from 5,000 yuan t0 80,000 yuan, according

to a recent report on the Yangzi Evening News. The fee (费用) is decided by university authorities based on

the popularity of each major, the report said. The most popular majors include computer science, law, finance,

information engineering and foreign languages.

     A saying popular among students may explain the phenomenon (现象). Studying a good major is much

better than studying in a famous university.

     Some educators warn students against rushing blindly to today's popular majors. They may not be popular

years later, the China Youth Daily said. But it seems that many students are career-oriented (以职业为宗旨的),

instead of being interest-based.

     Freshmen are allowed to change to other departments, according to rules of the Ministry of Education. But

there is no official rules on the charges. In spite of the high charges, demands to change majors are still

increasing. The paper said about 100 students in the English language department of a school in Harbin changed

from other departments. The department planned to admit only 50 freshmen this year.

     These charges have become a big income for some universities, the paper said. It is expected a normal

school in Harbin will get an income of 30 million yuan this year.

1. Xiao Wang would rather pay 20,000 yuan to choose the Economics Department because _____.

A. her parents have persuaded her to do so

B. she prefers to study the major

C. it has a promising future

D. transferring to another major is very popular in university

2. The following are the most popular majors in China today except _____.

A. law

B. computer

C. English

D. teaching

3. The fees that freshmen hand in to change to a new major are decided by _____.

A. headmasters

B. the Ministry of Education

C. university authorities

D. the China Youth Daily

4. The writer wrote the passage to _____.

A. encourage students to change to popular majors

B. explain that is not right for universities to charge too much money

C. tell us a new phenomenon that took place in universities

D. warn the students to be careful if they want to change majors

屋顶的坡度是如何确定的？

60岁，起病较急，头晕，一侧肢体无力麻木，数小时即消失，过去有类似发作，该患者诊断为何病（）

A．腔隙性脑梗死

B．短暂性脑缺血

C．脑血栓形成

D．脑栓塞

E．脑出血