人教版九年级下册英语Unit 13第5课时Section B 3a～Self Check课时作业本答案
1Section B 3a～Self Check第一题答案
（一）
1、 litter
2、plastic
3、recycled
4、ecosystem/environment
5、 harmful
6、 chain
7、takeaway
8、cost
9、industry
10、transportation
11、wooden
12、metal
（二）
1、advantages
2、cruel
3、 bins
4、chains
5、creativity
2Section B 3a～Self Check第二题答案
（一）
| 1 | 2 | 3 | 4 | 5 |
| C | B | A | D | C |
（二）
1、has； been polluted
2、 heard of/about
3、was discovered
4、for； to live in
5、used to sing
3Section B 3a～Self Check第三题答案
（一）
| 1 | 2 | 3 | 4 | 5 |
| E | A | F | C | G |
（二）
One possible version：
As we all know， plastic bags are bad for our life. They may fly with the wind and make the environment ugly. And animals may eat thetn by mistake and die. With plastic bags in the fields， crops can't grow well. Besides， burning plastic bags gives out harmful gases and pollutes the air. So trying to use fewer plastic bags is important.
I think all the shops should stop offering free plastic bags. We should try to use cloth or paper bags instead of plastic ones when shopping. What's more，whenever we see plastic bags on the streets or in the fields，we should pick them up and put them into dustbins. If everyone can use fewer plastic bags，we are sure to build a more beautiful city.