He found ______ very helpful to memorize the words of some popular English songs.

Can he work out the maths problem? —-I think _____ hard for him to work it out.

Whose book is this? There is no name on it.—Let me see. Oh, it’s . I lost it a few days ago.

Wal-mart isasupermarket______we can buy many expensive or inexpensivethings.[ ]

____ __ have you been at this factory? — Since 2000.