以下说法正确的是?() A.在电场中,电场强度大的点,电势必高。 B.一带电粒子

题型:选择题

问题:

以下说法正确的是?(    )

A.在电场中,电场强度大的点,电势必高。

B.一带电粒子只受电场力作用,在电场中运动时,电势能一定变化。

C.电场中电场强度大的地方,沿电场线方向电势降落快。

D.电荷置于电势越高的点,所具有的电势能也越大。

考点:电场强度的定义式
题型:选择题

阅读短文,选择正确答案。

     "Tom? Are you in bed yet?" called Mrs.White. There was no answer. Mrs. White put down her book and

went to her 14-year-old son's room. Tom was sitting in front of a bright computer screen on which a motorbike

was running fast.

     "Oh, Tom. You're still playing on that computer game. You must stop now, it's half past eleven. If you don't

go to bed soon, you'll be very tired tomorrow," said Mrs. White. 

     "But I've nearly won the game," Tom said to Mrs. White. She could see the excitement on his face. She sat

down beside him. 

     "You're always playing on the computer. You spend more time on this machine than on your homework."

      Today more and more families have computers. Parents hope computers can help their children improve

their study at school. But many of their children use computers to play games and watch videos instead of

studying. We often see that computer net bars are crowded with people, especially young boys. They spend a lot

of money competing (竞争) with the computerized (用计算机控制的) machines. The more they lose, the more

they want to win. The result is that they don't want to work or study.

     In some countries, even scientists hate computers. They say computers cause millions of people to lose their

jobs or cause them a lot of trouble. Computer game addiction (瘾) is a serious problem in social (社会的) life.

Something has to be done to solve the problem.

1. How did Mrs. White feel when she saw her son playing late? [ ]

A. She felt excited.

B. She felt happy.

C. She felt worried.

D. She felt wonderful.

2. Parents hope computers can _______. [ ]

A. help their children improve their study at school

B. help their children play well

C. help their children know a lot of Internet knowledge

D. help their children relax themselves

3. Many children use computers to _______. [ ]

A. watch videos

B. listen to songs

C. play games

D. A、B and C

4. The writer thinks _______. [ ]

A. the boys can go to the computer net bars, but the girls can't

B. the computer net bars are very useful

C. the children spend too much money on computer games

D. the children should play computer games

5. Why do some scientists hate computers? [ ]

A. They think computers cause millions of people to lose their jobs.

B. They think computers cause them a lot of trouble.

C. They think it's a waste of time to use computers.

D. Both A and B.

题型:选择题

简述混浊果蔬汁。

题型:选择题

对我国植被资源破坏性最大的是___________、_______、_______等。

题型:选择题

男性,20岁,左前胸刀刺伤后半小时,送至急诊室时,面色苍白,呼吸困难,血压不能测得,心率150次/分,颈静脉充盈,左肺呼吸音低,心跳很快停止。此时应采用下列哪项紧急处理措施?()

A.立即胸腔穿刺排气

B.心包穿刺后送手术室

C.胸外心脏按摩

D.动脉输血

E.就地气管插管,开胸手术探查

题型:选择题

心肌梗死时发热一般出现在()

A、与胸痛同时出现

B、在胸痛发生后12-24小时

C、在胸痛发生后24-48小时

D、在胸痛发生后36-72小时

E、在胸痛发生之前

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