Who teaches _______ English?
The rivers will become dirtier and dirtier ______ we take action to protect them.
He is an honest boy. I have no reason to _______ what he said.
-- It will be my turn. I feel a little nervous. --________ You can make it!
-- What was Jim wearing at the party?-- Nothing ________. He was in his usual shirt and jeans.
—It's so late. Why not write the report tomorrow? —But I don't know _______. I can do it if not now.