A. Our team is better than theirs.
The common noun is: Team.
B. They want to buy books and bags.
The common nouns are: Books, bags.
C.The elephant has great strength.
The common noun is: Elephant.
D. Petrol is called the liquid gold.
The common nouns are: Petrol, gold.
E. A committee of five was appointed.
The common noun is: Committee.