题目内容：

What do you do if you are in trouble on a lonely island? Surely you need to find a way to get in touch with the outside world. Your best chance of doing this is to draw the attention of a passing plane.

Body signals

Pilots from different countries understand body signals if they have the correct training. When you wave your arms up and down in a straight line, it means “yes”. When you point downwards and swing your arm from side to side, it means “no”. If you want the pilot to know that it’s safe to land, push your hands in front of you and bend your knees. If you want to say it’s not safe to land, put your arms in the air and move them to one side.

Smoke signals

The smoke from a fire can be seen from far away, so it’s a good way to draw attention. If the weather is dry, it isn’t hard to start a fire. Remember, however, the fires can be very dangerous if they get out of control. Never light a fire unless you are sure that it can’t spread. If the ground is dark, light smoke can be seen more easily. Green grass and leaves produce light smoke.

Ground-to-air signals

It’s a good idea to build some signals, too. Use large pieces of wood to make the symbols. If you can’t find any wood, use earth. Some useful symbols are：

F   “I need food and water.”

II   “I need medicine.”

I    “I am badly hurt.”

X   “I am unable to move from here.”

Pilots’ replies

If the pilot lowers the plane’s wings from side to side, this means “message received and understood”. (At night, the pilot flashes the plane’s green lights.) If the pilot flies the plane in a clockwise (顺时针方向的) circle, this means “message received but not understood”. (At night, the pilot flashes the plane’s red lights.)

However, there is no signal which means “message not received”．

1.Which picture means “it’s safe to land”？

A. B. C. D.

2.What can you use to build Ground-to-air signals on a lonely island?

A.Wood or earth. B.Grass and leaves. C.Wood and leaves. D.Sand or grass.

3.What is the passage mainly about?

A.The explanation of body signals on an island.

B.The importance of making signals on an island.

C.Ways of living on a lonely island.

D.Ways of sending out signals on a lonely island.