____________ you are sure there are no gas leaks, don't light any matches.
A. If
B. When
C. As
D. Unless
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It’s a waste of time with such a silly fellow.
A. trying to reason
B. tried to reason
C. for trying to reason
D. to trying reasoning
Franklin’s ability to learn from observations and experience greatly to his success in public life.
A. contributed
B. contributing
C. contributes
D. contribution
Only ____________ of the United States may vote in the election.
A. persons
B. people
C. citizens
D. natives
Homework on time will lead to better grades.
A. done
B. be done
C. having done
D. to have done
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