The true statement regarding credit cards is:
They can be used to make online purchases.
The other statements are not accurate in the context of how credit cards work. You can use a credit card to make purchases even if they exceed the amount you have in the bank, and while interest rates can vary, they can be significantly higher than 3% to 5% depending on the card and the user's creditworthiness. Additionally, users can track their spending and know how much they owe when using a credit card.