试述肝性脑病的诱发因素。

The rockets take astronauts and man-made satellites into space. The satellites are used for communication, weather monitoring and research. But how do satellites stay up without falling down?

There are two opposite forces (力量) acting on the satellite. One of them is the force of gravitation (地心引力), which tries to pull the satellite towards the earth. The other force is created by the rotation (旋转) of the satellite around the earth. This force tries to take the satellite away from the earth. With these two forces, the satellite goes round and round. The gravitational pull of the earth (the force which pulls everything towards the ground) is like a rope which keeps the satellite from flying away.

Everything that goes up has to come down. It is only a matter of time before a satellite comes back to the earth. As time goes by, the satellite loses its speed, which makes the gravitational pull stronger than the force pulling it away. This makes the satellite crash (坠落) down to the earth.

小题1:Which of the following uses of satellites is NOT mentioned?

A．communication

B．monitoring the weather condition

C．doing some research

D．taking pictures小题2:The force that pulls the satellite towards the earth is created by ________.

A．the earth

B．the satellite itself

C．the rotation of the satellite

D．the rope小题3:Why can’t the satellites fly away?

A．Because of the force from the earth.

B．Because the satellite is too big.

C．Because of the force created by the rotation of the satellite around the earth.

D．Because people on earth have made ropes to tie the satellites tightly.小题4:The satellite will finally crashes down to the earth ________.

A．when it flies faster

B．when its speed slows down

C．when people cut the rope

D．when there is no electricity in it小题5:Which of the following is TRUE according to the passage?

A．There are four forces acting on the satellite.

B．The force of gravitation makes the satellite go round and round.

C．As time goes by, the satellite will finally fall down.

D．The satellite will stay in space forever.

在凸透镜成像的实验中，发现光屏上形成的烛焰的像不清晰，请写出两种能使屏上烛焰像变清晰的方法：    

(1)_________________;

(2)_________________．

如图是火箭发射升空时的情景．（填物态变化名称）

(1)火箭点火后，发射台附近产生了大量“白气”，这是台下导流槽内的水在高温火焰下发生物态变化，先______成水蒸气，然后________形成小水珠。

(2)为保证飞船返回时安全，船体上涂有一层特殊固体物质，在高温下，先______然后________，这两个物态变化过程都需要吸热，以防温度过高。

近些年来外来入侵物种（如：加拿大—枝黄花、巴西龟、水葫芦等）对我国生态环境、农林业生产和人们身体健康造成严重威胁。据此回答26—27题：

小题1:外来生物入侵某一区域，极易造成“疯狂繁殖”的原因是（  ）

A．繁殖能力强

B．营养源丰富

C．缺乏天敌

D．生物竞争激烈小题2:下面四幅统计图中，能反映水葫芦大量繁殖对水体DO（溶解氧）、BOD（生物耗氧量）产生影响的是（  ）

固体燃料、液体燃料及气体燃料对环境污染最小的是（）。

A、固体燃料

B、液体燃料

C、气体燃料