1. Because of her laziness, she failed in her exam.
Because .... she was lazy, she failed in her exam. 
2. He broke the vase because he was careless.
He broke the vase because of his carelessness. 
3. She couldn't come to class because of her illness.
Because she ...... was ill, she couldn't come to the class. 
4. He couldn't go to school because of his sickness.
Because he ......was ill, he couldn't go to school. 
5. Because the weather was bad, we stayed at home.
We stayed at home ......because of the bad weather. 
6. Because it rains, they can't go shopping.
They can't ...shopping because of the rain. ........
7. He bought this car because of its price is low.
He bought .....this car because it is cheap. 
8. It rains heavily, so we can't go out.
Because of .......the heavy rain, we can't go out. 
9. She was lazy, so she couldn't pass the exam.
Because of ..... her laziness, she couldn't pass the exam. .
10. Nobody can do the test because its difficulty.
Because the test is difficult, nobody can do it.