Which of the following is a source of credit?

Credit cards are indeed a source of credit because they allow individuals to borrow money up to a set limit to pay for goods and services. When someone uses a credit card, they are essentially taking out a loan that they are expected to pay back within a specific timeframe. Credit cards offer flexibility and can help build a credit history if managed responsibly, which is crucial for future borrowing, such as obtaining loans or mortgages.

The other options do not serve as sources of credit in the same way. For instance, cash advances are a method of accessing funds on a credit card, but they do not inherently function as a separate credit source. Gift cards, on the other hand, are preloaded with a certain amount of money and cannot be used to borrow beyond that limit; they do not involve credit at all. Bank checks are simply a method for transferring funds from an account and do not represent borrowing or credit either.