请根据下面的实验过程给图排序，将其序号填入第66 ～69空格中，并完成第70小题。Do the experiment as follows ：
【小题1】（ ）Put a short (0. 5 meter) board on two books. The books should be under the center of the board.
【小题2】（ ）Ask your partner to stand on one end. With your hands ， push down on the other end. Can you lift your partner?
【小题3】（ ） Put a longer (1 meter) board on the books. The end should be about 30cm from the books. Have your partner stand on the end that's near the books. Can you lift your partner?
【小题4】（ ）Now do the same with the longest (2 meters) board. The end should be half a meter from the books. What will happen? Yes ！ You can lift your partner easily ！

【小题5】What experiment is it?

请根据下面的实验过程给图排序，将其序号填入第66 ～69空格中，并完成第70小题。Do the experiment as follows ：

1.（  ）Put a short (0. 5 meter) board on two books. The books should be under the center of the board.

2.（  ）Ask your partner to stand on one end. With your hands ， push down on the other end. Can you lift your partner?

3.（  ） Put a longer (1 meter) board on the books. The end should be about 30cm from the books. Have your partner stand on the end that's near the books. Can you lift your partner?

4.（  ）Now do the same with the longest (2 meters) board. The end should be half a meter from the books. What will happen? Yes ！ You can lift your partner easily ！

5.What experiment is it?

A. A chemistry experiment.        B. A physics experiment. 

C. A math experiment.            D. A medical experiment.

Have you ever heard an echo of your voice?

An echo is a reflected(反射)sound. Stand in a very large, empty hall with nothing on the walls. Then shout. The sounds you make will hit the walls and come back to you. The walls reflect the sounds. These reflected sounds are called “echoes”.

We can use reflected sound to make sound travel farther. Hold a watch about fifty centimeters from your ear. You cannot hear it. The sound of the watch travels a short way in all directions. It does not travel as far as your ear. You can make it travel to your ear by using a roll of cardboard(纸板筒).

Make the roll of cardboard about fifty centimeters long. Put one end over your ear and hold the watch at the other. Now you can hear the watch because the sound has not gone in all directions. It is reflected down the roll to your ear.

A megaphone(喇叭筒)works in the same way. It makes sound travel farther. It reflects the sound into a beam which can travel a long way. In the ship, the sailor uses the megaphone to make his voice travel. Without the megaphone, his voice cannot travel far.

We use reflected sound in many ways. We use it to measure the depth of the sea, for example. Among the animals, bats and whales use reflected sound to tell them where they are and what things are near them.

1.What is called “echo”?

A．Very loud voices.

B．Very loud voices that are made by man.

C．Very loud voices that are made by animals.

D．The sound that is made by man or animals comes back from some place.

2.We can hear our echoes if we     .

A．shout in a small room

B．shout in a large house full of things

C．shout in narrow valleys(山谷)

D．shout in the open air

3.Which is the right order of hearing our echo in a very large, empty hall?

a. We hear the reflected sound

b. The sound returns to us

c. The sound hits the walls

d. We make a sound

A．c, b, a, d          B．c, a, b, d           C．d, c, b, a           D．d, b, c, a

4.From the text we learn that __________ .

A．reflected sound is useful only to blind people

B．people haven’t made use of reflected sound yet

C．bats use reflected sound to fly and get food

D．whales don’t use reflected sound as they live in the sea

5.If you haven’t got a megaphone, ____ will help you to make your voice travel farther.

A．a long piece of wood                     B．a roll of cardboard

C．a thin thread                           D．a long piece of silk