the middle of the 21st century , thevast majority of the world’s population ________ in cities rather than in thecountry.

_____ he had never worked so hard in his life. [ ]

He is always______fault with other people though he doesn’t do his own work properly.

The problem is not_______so easy as you think It’s far from being settled

We must do something so that there will be _____ pollution in our city.