What do you do if you're stranded（处于困境的）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（信号）
　　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 out in front of you and bend（弯曲）your knees. If you want to say that 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, that fires can be very dangerous if they get out of control. Never light a fire unless you're 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(标记). 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 pilots flies the plane in a clockwise 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". Why not?
【小题1】 Which picture means "it's not safe land"?

　
【小题2】 What can we learn from the passage?

What do you do if you're 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 (信号)
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 out in front of you and bend (弯曲) your knees. If you want to say that 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, that fires can be very dangerous if they get out of control. Never light a tire unless you're 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 lo build some signals, too. Use large pieces of wood to make the symbols (标记). 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 lo 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 circle, this means "message received hut not understood" (At night, the: pilot flashes the plants red lights.)
However, there is no signal which means "message not received. Why not'?
【小题1】How many signals can we use to draw the attention of the passing plane if you're in trouble?

It is reported by Chinese Xinhua News that students waste more food than the national average. So the campaign on school food waste is getting popular across the country. The move is part of a national campaign started by students at different schools.
At East China University of Science, students who finish their food in the school dining hall get a special card when they return their plates after meals. Students can collect cards and exchange them for small gifts, such as books, schoolbags, magazines and umbrellas. “It’s been such a surprise,” said Liang Zhaoyun, 19, a student in Shanghai. “It has given us one more motivation to eat up our food.”
“The purpose of the campaign is not only to encourage students to finish their food. We hope it can also teach students to choose a more environment-friendly and healthy lifestyle,” said Tao Siliang from University of Traditional Chinese Medicine.
Other schools also pay attention to the quantity of food. At Nanjing No.9 Middle School, rice is divided into three different-sized bowls that students can choose from according to their own need. “It’s great because I can try different dishes at half price and don’t waste so much food,” said Fan Peng, 15, a student from this middle school.
What if you really can’t finish all your food? At Changchun Normal College, they provide a take-away service. “If you can’t finish all your food, you can get a box to take the left food home. Even if you feed the cat, it’s not wasted,” said Zhou Zeyong, a student who learns Chinese education.
“I’m happy that we’ve cut down waste since joining the school ‘eat-up’ meeting. But some food is poorly cooked, meaning that students are not willing to finish it all. Some schools have taken note of this. So if we hope students try to waste less food, we should also improve the service and keep an eye on the meal quality on weekdays at school. If not, you can’t complain students for throwing away much food,” said Wang Guangji, the head-teacher of Beijing No. 29 Middle School.
【小题1】Why did we start the campaign on food waste at schools?  Because __________.