enjoys + V-ing 
She enjoys skating in her free time
dangerous + to V
It's dangerous to swim in the rivers
I hope he will pass the final exam (tương lai đơn)
Look at those black clouds It is going to rain (tương lai gần)
They'd better not swim here because it's dangerous

Đáp án + Giải thích bước giải:

1. She enjoys skating in her free time

→ enjoys + V-ing 

2. It's dangerous to swim in the rivers

→ dangerous + to V

3. I hope he will pass the final exam 

→ thì TLĐ: S + will + V0 + ...

4. Look at those black clouds. It is going to rain 

→ thì TLG: S + be + going to + ...

5. They'd better not swim here because it's dangerous

→ had better + V0: đưa ra lời khuyên người khác nên hoặc không nên làm điều gì

→ sau not + V0