To understand why the Earth is warming up , first of all, we need to understand why it is warm. Our planet is covered with atmosphere(大气) . Sunlight passes through the atmosphere and reaches the Earth. The Sun heats up the Earth’s surface. When the heat rises into the air, it is stopped by some special gases(气体) in the atmosphere like CO₂ , the heat returns to the Earth and keeps it warm.
Power stations and cars release (释放) so many greenhouse gases every day. So we can help stop global(全球) warming by using less electric things such as turning off lights when we leave a room, asking our parents to turn down the heating in our house to save energy. We can also stop global warming by finding other ways of transportation. For example, ride a bicycle or walk instead of going by car. Another way to help stop global warming is to plant and care for trees. Because trees take in CO₂ , they are our best friends when fighting against global warming.
The problem of global warming cannot be solved in a day. It may take a long time to find clean energy, such as wind energy. It may take a long time to plant the trees again we are cutting down. But every little thing each person can do to save energy and our forests will help. Think about our planet. Think about ways we can help make the Earth a safe and comfortable place for the future.
The underlined word “it” means _______ in the first paragraph.

A．the heat	B．the Earth
C．the sunlight	D．the atmosphere

_______ ways are mentioned to stop global warming to the second paragraph.

A．Two

B．Three

C．Four

D．Five

Which of the following is NOT true?

A．Everybody can help save energy and our forests.

B．The problem of global warming can not be solved.

C．To find clean enrgy will help solve the problem of global warming.

D．The writer wants us to pay attention to the problem of global warming.

Which is the best title of this passage?

A．Why is the Earth warming up

B．When can we stop the Earth from warming up

C．How can we stop the Earth getting warmer

D．How long will it take to stop the Earth getting warmer