如图1，将正方形纸片ABCD对折，使AB与CD重合，折痕为EF．如图2，展开后再折叠一次，使点C与点E重合，折痕为GH，点B的对应点为点M，EM交AB于N．若AD=2，则MN=____．

今年4月，我市某中学八年级的一名学生出现高烧、咳嗽、咽喉痛等症状后，陆续有多名学生出现类似症状。经医生诊断，他们患上了同一种传染病，该病通过空气飞沫在人群中传播。

The population of the Earth is growing faster. It is important that we look after the Earth. We need it!
The Earth gives us a lot of things. We also give the Earth a lot, but some of the things are not good.
In nature, when something dies, other animals and plants get food from it. Every animal or plant gives food for other animals or plants. However, animals can’t get food from many of the things that we ‘give’ the Earth. Animals and plants can’t eat metal, plastic and glass. These things will stay in the ground for many, many years.

Some rubbish is very dangerous for plants and animals. In some places, many animals live together. One animal makes food for many more animals. If we put rubbish and chemicals in the water, the plankton(浮游生物) can die. If there isn’t any plankton, many animals have nothing to eat.
So what can we do? Don’t leave any rubbish in the countryside! Don’t make so much rubbish!