We will go for a picnic if it ______ tomorrow.

We must keep the classroom ___________.

The water is too hot. We’d better       right now.

---The books are so nice. Which one can I take?---Oh, you can take __________ of them. I’ll keep none.

---How do your parents usually go to work?---My mother usually goes to work _________  bus while my father ________ a bike to work.