bài 1,2 là cặp và kt

bài 3

a.1-c

   2-a

   3-e

   4-b 

   5-d

b.

1. Two. They are renewable and non-renewable.

2. Hydropower is limited because dams can not be built in certain areas. Nuclear power is dangerous.

3. Because they are natural sources of energy and we use them instead of non-renewable sources.

4. We use non-renewable sources of energy the most but we are increasingly using hydropower.

5.He thinks Vietnam will use the wind and the sun as alternative sources of energy in the future.

 bài 4 làm theo cặp

bài 5

- Wind power is a renewable source of energy because it is free. It comes from wind. It's abundant. Unfortunately it isn't always available and it isn't cheap.

- Coal and natural gas is a non-renewable source of energy because it can be used up. If s very cheap but it's polluting. It's not friendly to the environment.

- Solar power is a renewable source of energy because it comes from the sun. It's abundant, clean and safe. Unfortunately it isn't cheap.