阅读短文，从各题所给的四个选项中，选出最佳答案。
Cars are lots of fun, but they could also be dangerous. We have to be careful when we drive them or ride in them.
It's always a good idea to put on your seat belt when you're in a car. Why? Think about this example: You put an egg on a skateboard and give it a push. If the skateboard hits a stone, it will stop, but the egg won't. It will fly through the air, hit the ground and break.
Now, think what would happen if you tied the egg to the skateboard. When the skateboard hits a stone, the egg won't go flying; it will stay safely on the skateboard.
Volvo, a famous Swedish carmaker, was the first to use seat belts in 1849.
Air bags are also very important for car safety, because sometimes a seat belt isn't enough. If the car is going really fast and runs into something, seat belts could even hurt the people who wear them. Most new cars have air bags in front of and next to the seats. When a car hits something, its air bags will come out quickly in less than one second to keep the people inside safe.
1. The passage mainly tells us .
A. two important ways to keep safe in cars B. how air bags work to make cars safe C. how seat belts work to make cars safe D. why we must tie the egg to the skateboard
2. The writer gives the example of the egg to _.
A. tell us that eggs are easy to break
B. show how to wear a seat belt
C. show why it's important to wear a seat belt in a car
D. tell us what a skateboard is
3. Seat belts can make us safer because .
A. we are interested in them
B. they can stop us from hitting other cars
C. they can help us stay safely on the seats
D. they are made of strong materials
4. Air bags are important for cars because _.
A. they are made of plastic
B. they can also help us to keep safe in a car
C. they can keep cars running slowly
D. they are put in front of and next to the seats
5. Which of the following is TRUE according to this passage?
A. It won't be dangerous if there are seat belts or air bags in a car.
B. Now most of new cars still have only one air bag.
C. When a car hits something, its air bags will come out a few minutes later.
D. Volvo was the first to use seat belts.