下列说法正确的是( ) A.反应热就是反应中放出的热量 B.当反应放热时ΔH>0

题型:选择题

问题:

下列说法正确的是(  )

A.反应热就是反应中放出的热量

B.当反应放热时ΔH>0,反应吸热时ΔH<0

C.一个化学反应中,当反应物的总能量大于生成物的总能量时,反应放热,ΔH为“-”

D.一个化学反应中,生成物总键能大于反应物的总键能时,反应吸热,ΔH为“+”

考点:能量的相互转化
题型:选择题

Earthquakes can be very scary(吓人的). But you need to keep your mind stable (坚定的) in order to make sure you are safe. Be calm and try not to run here and there.

If you manage to come out of your house, go to an open space like a garden or a park where you will be a lot safer. If you live quite some floors above in your building, try to find a place near a bulky(坚固的) object such as a bed. Curl up (蜷缩) and sit on the floor and make sure you are not near a window, fireplace, gas stove and so on. Remember don’t use lifts or escalators.

Some people say you should stand on a doorway. That is not true. If the doorway jambs (侧壁) are weak, they might fall on you. Also if people want to pass through that door, you may stop them. Leave all doorways free.

Another important thing to keep in mind is that you mustn’t climb down the stairs during an Earthquake. If the tremors (震动) stop, after a few seconds, just climb down the stairs as quickly as you can and move out of the building, but don’t run.

Earthquakes usually destroy gas pipes and electrical wires. Turn off the main gas. And don’t light candles or lighters and create an even bigger disaster.

If you’re driving and feel a shake, stop your car at the side of the road and get out. Make sure you are not on a bridge. Bridges and overhead roads (高架路) have the biggest danger of falling.

小题1: The best title for the passage should be       .

A.Dos and Don’ts Before an Earthquake.

B.What to Do in Case of Earthquake

C.Tips for Earthquake Preventions

D.Tips for Children in Earthquake.小题2:When an earthquake suddenly happens, you should       .

a. remain standing near a window             b. turn off the main gas

c. stay in an open space                     d. stand on a doorway

e. keep off  overhead roads

A.a, b, c

B.c, d, e

C.b, c, e

D.b, d, e小题3: Which of the following is NOT true, when an earthquake suddenly happens?

A.We can’t use the lift.

B.Curling up may be very dangerous.

C.We must turn off the gas.

D.We must get out of the car when the earthquake comes小题4: It can be learned from the passage that     .

A.keeping calm in time of earthquake is very important.

B.measures should be taken to make buildings stronger.

C.Knowledge of first aid must be used in an earthquake.

D.lots of things must be done to survive an earthquake.

题型:选择题

生物对环境的适应:每一种生物都具有______环境的能力(适者生存),生物对环境的适应不仅表现在______方面,还表现在______等各个方面.如形态上适应的有拟态、保护色等;______上适应的有鸟有鸟翅、鱼有鳍等;______上适应的有:鸟类迁徙、夏眠等.

题型:选择题

在Windows 98中,注册表的值可保存的数据类型除了字符串和二进制值外还有 ( )。

A.时间

B.日期

C.DWORD

D.整数

题型:选择题

若-a3b2m与4anb4是同类项,则m+n=(  )

A.5

B.1

C.7

D.-7

题型:选择题

蛤蚧的性状鉴别特征是

A.全身密被类圆形微有光泽的细鳞

B.脊椎骨及两侧侧肋骨突起

C.四足均有五趾,均具爪

D.趾底面具吸盘

E.尾细长而结实,扁圆形,有不甚明显的银灰色环带6~7条

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