Give the correct form of the word in brackets to complete each sentence

Ex3. Give the correct form of the word in brackets to complete each sentence.
1. A lot of toys encourage children’s . (imagine)
2. The factory has provided cheaper lately. (produce)
3. Burning coal is an way of heating a house. Gas is much cheaper.
(economy)
4. According to some scientists the earth is losing its outer atmosphere because of
__________________.(pollute)
5. She has one of the biggest art in Britain. (collect)