______ metals are good conductors, silver ______ the best conductor of all.
Both parents and teachers work hard at either preventing failure or protecting the children from the knowledge_______ they have failed.
—What a pity! You should have urged him to hand in his English homework. —I _______. But he wouldn’t listen to me.
As we all know, the world’s supplies of oil_________ up with the development of industry and the increase of cars.
It is reported that some wild animals were found_______ in a big cave in the mountain.
.We’ve published large quantities of books. This year______ we’ve published three million copies.