The Earth has warmed by about half a degree（0．50℃）over the last 100 years．It could be getting warmer on its own，but many scientists think that people are making the Earth warmer by making a greenhouse effect（温室效应）．The greenhouse effect is important． Without it，the Earth would not be warm enough for us to live on．But just a little warmer than it is now could cause（引起）problems for humans，plants and animals．

Many of the things we do every day can change the Earth’s temperature by sending greenhouse gases（废气） into the air．We send greenhouse gases into the air When we watch TV，turn on lights，dry hair，play video games，wash or dry our clothes or drive cars．The rubbish（waste） from factories and homes also produces greenhouse gases．

Even a small change in temperature can affect （ 影响） our weather．This can cause changes in the sea levels，the air，flooding，and our fresh water．

The change in the temperature can also cause changes in the living places for animals and plants，endangering many animals．

Global warming（全球变暖） is a big problem，and every little bit we do can help．We can save electricity．We can save energy in other ways such as by taking buses or walking rather than driving cars．We can recycle to reduce the rubbish and save natural resources such as trees，oil and metals．We can buy products that don't do bad to the environment and we can turn to solar energy．Remember the little bit that you do will bring a better world．

1．Which of the following does not send greenhouse gases into the air?

A．Turning on a light．                        B．Walking to school．

C．Driving a car．                           D．Watching TV．

2．In this passage，the scientists are mainly trying to make the readers realize___________

A．the earth could be getting warmer by itself   

B．the earth is getting warmer in 100 years

C．the greenhouse effect is important

D．humans are making the earth warmer

3．Without the greenhouse effect，we would_____________

A．not be able to live                        B．be safer

C．have a cleaner earth                      D．have a better world

4．The writer gives us advice on how to save energy in __________

A．Paragraph 2        B．Paragraph 3         C．Paragraph 4        D．Paragraph 5

5．Global warming is a big problem but ___________

A．we can't do anything to help                B．we don't need to do anything

C．we can do something to help               D．we can do something to stop it