—Who______ it be that is knocking at the door? —It ______ be Father, but I’m not sure.
It will take a lot of time and_____ to finish the task on time.
We’ll have our picnic in the place _____ most of us like best.
My house _____ when you visited Beijing last time, so I didn’t invite you to my home.
She had to drop out of school _____ her family couldn’t afford the cost of her education.
The old man has retired from the factory. He _____ there for 30 years.