---Someone is knocking at the door. Who may it be? ---It ______ be Tom. He is still in the school.
---Have you returned the book to the library _______?---Yes, I have _______ retuned it.
---Do your parents have the same hobby?---No.My father likes playing____ football while my mother enjoys playing _____piano.
My parents are always strict________ me.
—Mom, my classmates invited me ________ a field trip. May I go with them? —OK.
—John isn’t happy today. Let’s go and ________. —Good idea.