---Look. The man at the gate _____ be our headmaster. He is always standing there every morning.---No. it ____ be him. He is having a meeting in the office now.
In the past few years there ________ great changes in my hometown.
To make our city more beautiful, rubbish _________ into the river.
— Does your mother often _______ to you?— Yes. But she always ________ the same words.
---The students of Class 7 are going to the seaside this weekend.---Remember _____ them not to keep _______ alone in the sea. It’s dangerous.
The twin sisters have learned a lot ________ they came to China.