1. Because the weather was so bad, we had to cancel the flight
We had to cancel the flight because of bad weather
2. He stayed at home because he was ill
Because of getting ill, he stayed at home
He stayed at home because of his illness
3. We can't stand him because he behaves badly
We can't stand him because of his bad behavior.
4. He didn't pass the exam because he was lazy.
He didn't pass the exam because of his laziness
5. Because the door is heavy, the boy can't push it open
The boy can't push the door because of its heaviness
6. They can't buy the house because it is too expensive
They can't buy the house because of its high price
7. She can do this exercise because the student is very intelligent
She can do this exercise because of intelligence of the student
8. The children couldn't go swimming because the sea was too rough
The children couldn't go swimming because of rough sea
9. He was sad because he failed the exam
He was sad because of his failed exam
10. He was happpy because he succeed in the final test
He was happy because of successful final test