1. Mary didn't go to school yesterday because she was sick.
=>  Because of Mary's sickness, She didn’t go to school.
2. She went to bed early because she felt tired.
=>  Because of feeling tired, she went to bed early.
3. Ann didn't go to the circus with Betty because she had a bad cold.
=>  Ann didn't go to the circus with Betty because of having a bad cold
4. John succeeded in his exam because he worked hard and methodically.
=>  Because of working hard and methodically, he succeeded in his exam
5. Margaret stayed home because her mother was sick.
=>  Because of her mother's sickness, Margaret stayed home.
6. I like him because his father is kind to me. 
=>  Because of his father's kindness to me, I like him/ or ( Because of his father is kinding to me, I like him)
7. I can't eat these fruits because they are green. 
=>  Because of being green, I can’t eat these friuts
8. I couldn't do the test because it was difficult.
=>  Because of being difficult, I couldn't do the test 
9. I couldn't read the letter because it was dark.
=>  Because of the darkness, I couldn't read the letter 
10. He came late because it rained heavily.
=>   Because of the heavy rain, He came late / or ( Because of it's raining heavily, He came late)
11. I can't study because it is noisy.
=>   Because of the noise, I can’t study.
12. The train came late because it was foggy.
=>   Because of the fog, the train came late.
13. All the teachers love him because his conduct is good.
=>  Because of  his good conduct, all the teachers love him
14. The train was late because the fog was thick.
=>  Because of the fog being thick, the train came late
15. We stopped our car because the traffic lights turned red.
=>  Because of the traffie lights turning red, we stopped our car
16. The plane couldn't take off because the weather was bad.
=>  Because of the bad weather, the plane couldn't take off 
17. Rice plants grow well because the climate is warm and damp.
=>  Because of the climate is warming and damp, rice plants grow well
18. He couldn't drive fast because the street was crowded and narrow.
=>  Because of the street being crowded and narrow, he couldn't drive fast 
19. I can't sleep because the weather is hot.
=>  Because of the hot weather, I can't sleep
20. He left school because his life was hard.
=>  Because of his life was being hard, He left school 
 Because of the his life's hardness, he left school.