---Look at the boy running on the playground. Is it David?---It ________ be him. I saw him go to the teachers’ office just now.
______ he tried many times, he still didn't move the heavy box.
What do you think “anxious” ______?
--What is your father like ? --_____________________.
If I felt some pain, I would stop _________.
--Does the bike belong to_________? ---No, it is ___________.