--When did your father come back last night? --He didn't come back _______ he finished all the work. A. until B. while C. if
—_______ are you leaving for Shanghai?—In a couple of months.
—This is _______ fascinating museum I have ever visited.—Yes. I’ve never seen a _______ one.
Stephen Hawking thinks _______ important to have hope in bad situation.
Robert is away. He _______ America since last week.
—Why are you packing so many books?—I’ll _______ to the kids in West China.