A credit card is a card that you can use to purchase items with borrowed money from a credit agency. It's usually used to buy items with huge sums (because why would you keep anything more than $100 in your wallet on an average day?), so buying movie tickets and purchasing gasoline are things you're more likely to pay cash for. Computers are always expensive items and without knowing where the groceries are bought or how much they cost, we can assume there are situations where you might not have to pay a lot for groceries. So I believe it would probably be better to use a credit card for C. Purchasing a computer (unless you have a lot of groceries). Hope this helps!