13. Because Vy ate a lot last night, she had a stomachache.
→ Because + S + V + (O).
14. Because of the dangerous acid rain, trees' leaves are damaged.
→ Because of + noun/ noun phrase
15. Leaves are damaged because the tree cannot get enough food energy to stay healthy.
16. Eating too much sugar can lead to health problems.
→ S + lead to + N
17. Tom said that his mom would write a letter to him.
→ S + say(s)/said + (that) + S + V

Chúc bạn học tốt! Nếu có thắc mắc gì thì bảo mình nha. ^^

`13.`Because Vy ate a lot last night, she had stomachache.

`=>`Because + S + V, S + V : Bởi vì...

- Dịch : Bởi vì Vy ăn rất nhiều tối qua, cô ấy đã bị đau bụng.

`14.`Because of dangerous acid rain, trees' leaves are damaged.

`=>`Because of + N/Ving, S + V : Bởi vì...

`15.`Because of damaged leaves, the tree cannot get enough food energy to stay healthy.

`=>`Because of + N/Ving, S + V : Bởi vì...

`16.`Eating too much sugar can lead to health problems.

`=>`cause `=`lead to `=`result in : gây ra

`-`Ở câu trên, ta chỉ gần thay "cause" bằng "lead to" và giữ nguyên các vế còn lại

- Dịch : Ăn quá nhiều đường có thể gây ra những vấn đề về sức khoẻ.

`17.`Tom said that his mom would write a letter to him.

`=>`Câu gián tiếp với "said" : S + said ( that ) + S + V lùi thì...

`-`will write `->`would write ( Lùi thì )

`-`my mom `->`his mom

`-`to me `->`to him