— I phoned you yesterday morning. A girl answered, but I didn’t recognize the voice.— Oh, it ____ my younger sister. She was in my room at that moment.

－Look, your sister is playing the piano over there.－She ______ be my sister. She has gone to America.

The city has changed little in the last        years. 

These books______very interesting. Many children like reading them.

It is usually warm in my hometown in April, but it ________ be rather cold sometimes.