29．—May I speak to your manager at three o’clock tomorrow afternoon ?—I’m sorry, He to Shanghai by then

We should________the lights when we leave our classroom because we must save electricity. [ ]

________you study , _________your parents are .

Time ____ never comes again. So we’d bettermake full use of our time.

__________ is known to all, China will he an ________ and powerful country in 20 or 30 years’ time.