While you are out, you should keep your doors and windows ___.
There were dirty marks on her trousers _________ she had wiped her hands.
. A modern city has been set up in _________ was a wasteland ten years ago.
. If Tim carries on working like that, he’ll _________ sooner or later.
What surprised me was not what he said but _________ he said it.
. The conference gives a chance for people of different _________ to exchange.