12．We will be shown around the city：schools，museums，and some other places，other visitors seldom go．

While ________ to foreigners，you must try your best to make yourself ________.

I think students may bring iPad to school.–_________ This can cause some trouble.

te many children’ s books, nearly half of____ were published in the 1990s.

Work gets done __________ when people do it togetherand the rewards are higher too