_________ useful invention the computer is.–Yes, It helps us a lot.

It was____ computer games that cost the boy lot of time that he ought to have spent on his lessons.

下列有关文学常识的表述，不正确的一项是（ ）

It is so crowded. Where is Jack—He is very tall. We can easily _____ himin the crowd.

Bears often hide themselves in places________ can’t be found by hunters.