Complete-the-argument questions involve two considerations. First, they are often disguised conclusion questions, so that we want to keep logical inferences and strict scope considerations in mind. Second, to a much lesser degree, we want to think about flow.
Here, the author mentioned two things in the argument, and they were both facts/premises. First, the author said that most people expect to pay their bills before interest accrues. Then the author said that credit card companies concentrate on the services their customers care most about when trying to win over customers from other companies. The first thing that comes to mind for me, and I’m guessing most readers, is that the customers probably don’t care too much about anything related to interest if they don’t plan to ever pay it. While common sense might dictate that you should care a little in the real world in case something unforeseen happens, this is LSAT logic we’re talking about.
Let’s take a look at the answers keeping in mind our conclusion but also staying open to other logically sound conclusions.
(A) is just silly _ it’s clearly unsupported by any of the statements above.
(B) sounds about right. This involves interest rates and what people do or do not want. Specifically it says what you might even have realized above _ that since interest rates are irrelevant to most people (at least according to their expectations), they probably won’t think about this in choosing a credit card.
(C) is out of scope _ there is nothing in the passage about borrowing money from banks.
(D) looks more like a new premise than a conclusion. We don’t have enough in the passage to support an inference about whether the period of time matters.
(E) has many indicators that it is not the correct answer _ "most intense" and also the introduction of a new idea _ the number of places who accept the card.
Interestingly, this is a pretty straightforward question if you work by process of elimination, even though it comes rather late in the section. That said, it was important here to keep in mind what we knew logically to be true, or we could have been misled with some of the trickier answer choices.