--- My son is _____ to be seen. Where has he gone? --- I think he _____ in the building.
The plan put forward at the meeting is________perfect;there’s still much room to improve.
—Any advice for me? —You’d better________the timetable to see when the train leaves.
—Do you ______ the idea of living a low-carbon life? —It sounds tough, but it is a tendency.
The first successful space walk in 2013 is an important historical________in Chinese history.
—Look! Someone ________ the floor. —Well, it wasn't me. I went shopping just now.