Hi S.C.!
Happy to try to provide some clarity on this one.
There are some markers in the stimulus that limit what is being discussed, specifically phrases that include:
- "According to my research,"
- "This research also suggests ..."
- "Therefore, my research would lead us ..."
In other words, the premises and conclusions are only about the author's research and what it shows. The author's research shows that most people in the research (59 percent) don't accrue interest. Faced with the task of making the most reasonable interpretation of just that aspect of the research, does it lend more support to the idea that a credit card's interest rate makes a huge impact or a negligible impact on those people? Even if we don't know answers to broader questions about whether interest rates actually impact people, we only need to be dealing with what can most reasonably be gleaned from the author's research alone. Certainly
that research points in the direction of negligible impact over huge impact.
In addition, the second sentence refers to what customers are "most interested in." Even if it were supposed that interest rates somehow impacted customers, surely the research doesn't point to the conclusion that interest rates are what they would be "most" interested in. That research finds that most people in the research never pay interest. Making the most reasonable interpretation of the research, does it really support to the idea that a credit card's interest rate is what people would be "most" interested in? This seems implausible.
That is why answer choice (B) is correct. (B) states that "credit card companies would not make the interest rates they charge on cards the main selling point." Most people in the research don't pay interest, and the research also suggests that companies want to target what they are "most" interested in. Taken together, the research suggests that companies will want to target something other than the interest rate.
It's possible that perhaps no one will in fact care about anything other than the interest rate and maybe this is what companies will eventually target anyways. But that's outside the bounded limit that this question deals with, which solely involve what can most reasonably be inferred about the author's research. It's also even possible that an interest rate impacts those people in the research (e.g., maybe it impacts their peace of mind, even though it doesn't have a financial impact), but that too is unnecessary to speculate about, for surely the research at least suggests that the interest rate is probably not the top on their list as the most important thing to find in a credit card.