________ of the city was covered with the heavy smog.

In ancient times, dogs were mainly ______helping people hunt( 打猎) .Now they are more useful-they can help the blinds, search for the bad eggs,…

_____you do, don’t miss this exhibition, for it’s so hard for me to get the tickets.

Danny is walking. He is __________ his way __________ home.[ ]

If he _____ free tomorrow , he ______ to see me .