Trees ________ every year to make our city greener.

---It’s difficult for the villagers to cross the river. ---I think a bridge______ over the river.

 —Wow! Your school is so beautiful!—Thank you! It _____ last year. 

— At present, one of the best ways to study is working in groups.—More chances _______ to students to learn from each other.

The park _________by the cleaners every two days.