Explanation

Reading the question: we read the statements of the columnist, which turn out to be a brief rant. We don't have to criticize what the columnist said; rather, we have to draw a conclusion. We can prove by stronger terms; most likely, the correct answer choice will be not only a good conclusion, but a required conclusion. Such a choice may not be the most natural conclusion, but it will be the most objectively flawless one. That's our filter.

Applying the filter: (A) does not follow from the prompt, which gives a lack of vigilance as a failure mode here, but not necessarily how we catch petty crime above all. (B) is neither indicated nor required by the argument. Same with (C). (D) sounds natural, but it need not be true. The columnist's point might be, for example, that we can't trust the chief at all, and need to demand his replacement. That leaves us with (E).

Logical proof: we can see that (E) must be true. If the police have caught fewer acts only because they haven't been trying as hard, then there are at least as many acts as before. We apply the negation test. Suppose that pickpockets do not carry on their petty crimes. Suppose there were no more pickpockets at all In that case, the decline in pickpocket cases cannot be attributed to poor vigilance. The correct answer is (E).