GMAT Sentence Correction (SC) | Re: A 1972 agreement between Canada and the United States reduce

There's no doubt about the OA: it is definitely D, and there is nothing wrong with this question (which really is an official GMAT question).

People get confused by this one because of the shifts in time. An agreement that took place in the past (described correctly in the past tense) had an effect on what we are now allowed to do (described correctly in the present tense). Similarly, I could say that a movie made in 1950 "changed the way that we see romantic love" or that a change made
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