The book is very interesting. I can't stop reading it

The book is very interesting. I can't stop reading it.
→ The book is so ___________________________________________

She was tired. She couldn't go to the party.
→ She was too ____________________________________________

He didn’t come to class because he was sick.
→ Because of _____________________________________________

Although it rained heavily, they went to school.
→ In spite of _______________________________________________

If we don’t protect the environment, we will regret it.
→ Unless __________________________________________________