Now most families have only one child _____ our country’s one-child policy.
We were deeply impressed by the schools ______ we had visited in this city.
—What should I do, doctor?—You should take more exercise ______ healthy.
—Maggie, why did you take a bus today?—Oh, I forgot to tell you about that. My bicycle ______ yesterday.
—Someone is knocking at the door. Who ______ it be?—It ______ be Victor. He went to London yesterday.
When the firemen arrived, the fire had been ______