21.Their _________ to enter the lecture hall has to be stopped because they haven’t got permission.
A. announcement B. attempt C. approach D. solution
22. ________ his writing with his listening, we find he is better at his writing.
A. Comparing B. Compared C. Compare D. To compare
23. With a lot of difficult problems ______ , the newly-appointed mayor is having a hard time.
A. settling B. to settle C. settled D. being settled
