EconomistGMATTutor wrote:The conclusion: The government office was more lax in enforcing drug-promotion laws between 1976 and 1980 than it was between 1971 and 1975.
The evidence: Between 1971 and 1975, the government office issued an average of 60 citations a year, and between 1976 and 1980, the annual average for issuance of such citations was only 5.

This argument clearly assumes that the reason for the drop from 60 to 5 citations was because the government was lax. Perhaps there was a different cause. For example, maybe there were simply fewer actual violations. This is what Choice A, the correct choice, takes care of. It says that the decrease was NOT because of a drop in actual violations. This strengthens the claim that, instead, the government was lax.

You asked about Choices B and E. Choice B is irrelevant. It says that there was a change in the enforcement of drug-promotion laws without saying what that change was. Were the laws more strictly enforced? Less strictly? The fact that this change did not apply to minor violations doesn't matter either.

Choice E is an "other" choice. Why does it matter that there were more than 60 citations a year prior to the period that is relevant to the argument. It doesn't.

I'm available if you'd like to follow up on this question.