I can’t tell when the house was built _______, but it must be very old.

How often doyou chat with your friends online?—. I’m busy with my study.

She was so _____in her job that she didn’t hear anyone knocking at the door. [ ]

1—It looks heavy. Can Igive you a hand—___________.

Like most of my schoolmates, I have neither brothers nor sisters – ______, I’m an only child [ ]