Which of the following best describes a credit card's interest rates?

The correct answer highlights that credit card interest rates are primarily influenced by an individual's credit score. This is crucial because lenders assess the risk associated with lending money through credit cards based on the borrower’s creditworthiness, which is represented by their credit score. A higher credit score typically leads to lower interest rates, while a lower score may result in higher rates. This dynamic is valuable for consumers to understand, as it can affect the total cost of borrowing when the card is used for purchases or cash advances.

In regard to the other options, interest rates on credit cards are not fixed and can change based on various factors, including market conditions and the card issuer's policies; they are also not limited to secured cards, as many unsecured credit cards exist; and interest is not a flat fee—it accumulates based on the balance carried on the card. Therefore, understanding the relationship between credit scores and interest rates can be a key factor in managing credit effectively.