Fighting an artificial greenhouse effect seems to be the greatest of environmental challenges, ________?
—Could I borrow your dictionary?—Yes, of course you ________.
—The room is so dirty.________ we clean it?—Of course.
—Next week we’ll have the final English exam.—Yes. Then, every minute must be made full use ________ English.
—Can I help you, sir?—Yes. I bought this radio here yesterday, but it ________.
A left-luggage office is a place where bags ________ be left for a short time, especially at a railway station.