--Growing population resulted in growing rubbish. --There is possibility that rubbish ________the major threat to human beings.

—Hi , Tracy , you look tired.  —I’m tried. I ______ the living room all day.

------Have you telephoned your father? ------- Yes. He ______back next year.

My daughter________ hard for more than one year to realize her dream joining the Party and now her dream comes true.

He _________ English for eight years by the time he graduates from the university next year.