2. -He is very young, so he can't go to school
3. -Because of the long text, I couldn't finish it in an hour (Because of + n)
    -Becauase the text was so long, I couldn't finish it in an hour
4. -It hadn't been for the awful weather, we wouldn't have had to cancel our picnic
5. -Nga was very tired after her trip, so she went to bed early
6. -In order to be a good runner, he practices running everyday (In order to + for O + to V, S V)
7. -Owing to her illness, she went to bed early. (Owing to + n)
8. - Because she didn't have enough time, she couldn't read the books
9. - As his life was hard, he left school
10. -  Her age prevents her from working hard
11. - It was very dark, so I couldn't see anything
12. - Nam's laziness made him failed the exam
13. - Because the weather is lovely, we spend the whole day in the garden
14. - Because the text is difficult, nobody can do it
15. - Because of the narrow road, two cars can;t pass each other