How long did you spend going through the jungle during the exciting vacation?—Going through the jungle _____us about three weeks.

He was able to play the piano________the age of four.[ ]

Your bedroom is so dirty. Would you please _______, Peter?—OK, mum. I’ll do it right away.

Listen ! Helen is singing in the next room.—It __________ be Helen. She is in Tianjin now.

_______ is this backpack? –It’s yellow．