Even if there is no scientific proof secondhand smoke causes cancer, there is no reason why nonsmokers should be forced to take this risk.
In the past ten years, great changes _______ in my hometown.
The third and last chapter _______ by Professor Chen.
-- No, I’m afraid he isn’t in. This is his secretary speaking. Can I help you? --- _______.
______ the plane have taken off on time? --- I’m afraid not. The fog was too thick then.
There have been many changes in _____ history of _____ English language.