—Jane, have you finished yourpaper?     —No, I      my sister with her homework all the morning.

The past two years ________ a sharp rise in oil price, which adds to the burden of auto transportation industry.   

With the help of high technology, more and more substances _________ in the past years.

——Is there any possible way to help them get rid of such a bad habit? ——To tell the truth, it’s very hard. But we_______ on this problem.

--- Would you like to______ Mr. Zhang’s lecture this afternoon? --- Sorry, I have a class meeting to______.