Explanation

Reading the question: we see that we have logical completion exercise. If more than one answer choice seems like a logical continuation, there will be clues in the sentence that make one logical continuation more logical, objectively superior to the other ones.

Creating a filter: the blank is part of the conclusion of the argument, marked by the word "therefore," but it comes after the word "since." It's a piece of evidence mentioned within the conclusion. Most logically, it will not introduce a random new piece of evidence, but will rearticulate the evidence that has been given above. Specifically, it will do so in the context of the conclusion sentence--in terms of the recommendation for the new department. So what belongs in the bank is something about how this new department is a great idea because right now the some loans are great, but others are harmful, and the situation is uncontrolled. So we expect something in the blank like "needs control."

Applying the filter: which answer choices are in line with that prediction? Too many, we find. We need to be more specific. What needs controlling? The bad banks, specifically. (A) matches that. (A) is in. (B) seems to match that, but then introduces credit cards out of nowhere, so (B) is out. (C) does not focus on the bad banks and is out. (D) focuses on bad banks, but a different practice they have other than what we are talking about, so it's out. (E) is fairly logical, especially after (B) through (D). But (E) really gives a reason why establishing a new department is a better way of curbing bad banks than other ways. That's not material to the conclusion, which is that establishing the new department "would benefit public well-being." (E) skips the point by saying that the new department would be avoid side problems without talking about why it would be good for its aim. The correct answer is (A).