(2013·山西省太原市统一检测)—David, the windows of the room are very dirty. ________ I clean them before we move in?—Of course.

（2014年安徽省合肥市高三第三次教学质量检测）33. Thousands of travellers in and outside Hefei were ______to the Peach Festival the first day it opened this year.

—Why didn’t you finish the task?      —I didn’t think it is ________ the effort.

Your son came to my class every day, but his attitude _____ he was not really interested at all.

The global warming is more and more serious，for which human beings ________.