--What do Li Lei’s parents do?--They _________ doctors.

Sometimes _______turns off the lights in the classroom because every body thinks somebody will do it.

(2013·新课标全国卷Ⅱ)It's an either­or situation —we can buy a new car this year or we can go on holiday but we can't do ________.

 Is this a book on farming? If so, I want to borrow      .

________with better communication ability is more likely to succeed in his career