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<li> Two possibilities:</li>
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<p>a) Active voice is preferable to passive voice, if both forms could be used. The original sentence is written in the passive.</p>
<p>b) “To reduce pollution” states a goal. The U.S. and Canada set limits with the goal of reducing pollution. Reducing pollution is the goal of the people, and not the goal of the limits–the limits are just the means of implementation. So the infinitive phrase stating the goal would ideally be followed immediately by naming the goal-setters.</p>