Thinking that her daughter was doing homework, the mother left the room, _____ .

—Has your son come back from abroad for the winter vocation?—Yes. But he stayed at home for only a week. Now he _____ back to college. [ ]

Please _____ and wait a while. We’ll begin our meeting soon.

It’stenyearssincethescientist________onhislife’sworkofdiscoveringthevaluablechemical

Seventy percent of the students _____ taken part in the work and seventy percent of the work _____been finished. [ ]