The noise of the desks _____ could be heard in the next classroom.
--- The light in the office is still on. --- Oh, I forgot _______.
“ Have you decided when ________?” “ Yes, tomorrow morning.”
She pretended _______ me when I passed by.
There’re so many kinds of tape-recorders on sale that I can’t make up my mind _____ to buy.
—How’s your tour around the North Lake? Is it beautiful?—It ________ be, but it is now heavily polluted.