1,After they had provided food, they cleared up the debris

2,New devices have been invented by scientists to help people live a longer life

3,If i had enough time,i would go on holiday this summer

After they had provided food, they cleared up the debris

Radioactive pollution is very dangerous since it can cause abnormal growth 

If I knew the answer, I could tell you

I.

1. Because factories produce waste and pour it into rivers and lakes, many rivers and lakes are poisoned.

Because of the production waste from factories, many rivers and lakes are poisoned.

2. They provided food, then cleared up the debris.

=>After they provided food, they cleared up the debris.

3. The local people have to use water from the polluted river. They don't have enough fresh water.

=>If the local people had enough fresh water, they wouldn't have to use water from the polluted river.

4. I'm not you, but I think you should recycle these plastic carrier bags.

=>If I were you, I should recycle these plastic carrier bags.

5. All flights had to be canceled as a result of the pilots' sudden strike. 

=>The pilot suddenly struck, so all flights had to be canceled.

6. You have to keep quiet if you want to stay here.

=>She told me that I had to keep quiet if I wanted to stay there.

II,

1. Water pollution is the contamination of bodies of water such as lakes, rivers, oceans, and groundwater.

2. Have American celebrated Thanksgiving Day on the Fourth Thursday of November since 1864?

3. Scotland is famous for its rich culture as well as its amazing natural beauty.

4. The Statue of Liberty in New York is a monument which symbolizes freedom.

1. I don’t know her number, so I don’t ring her up.

→ If ……………………I knew her number, I would ring her up……………….....….…………………………….

2. There was a loud noise next to my door last night, so I couldn’t sleep.

→ Because ……………there was a loud noise next to my door last night,  I couldn’t sleep.……………………………………………………

3. They provided food then cleared up the debris.

→ After ……………… they had provided food, they cleaned up the debris. ………………………………………………….

4.Someone has stolen by bicycle.

→ My bicycle ……………has been stolen………………………………………………….

5.It was the first time I had been in an earthquake(never)

-> I…………………had never been in an earthquake before…………………………………….

6. I’m not you, but I think you should recycle these plastic carrier bags. ( if)

->………………If I were you, I would recycle these plastic carrier bags……………………………………………………….

7. if / I / Nam / I / not / use / this car / very often.

->………………If I were Nam, I wouldn't use this car very often……………………………………………………

1. After providing food, they cleared up the debris

2. If the people protect the environment now, the environment will be nicer

1. Smoke from mills, factories and industry can cause health problems like asthma and lung diseases. (lead)

=> Smoke from mills, factories and industry can lead to health problems like asthma and lung diseases.

2. Although the weather was bad, the football match wasn't cancelled. (Despite)

=> Despite the bad weather, the football match wasn't cancelled.

3. Peter is so kind to help the injured people (it's)

=> It's kind of Peter to help the injuried people.

4. They provided food then cleared up the debris

--> After they had provided food, they cleared up the debris.