Which of the following cannot be purchased by credit card?

Money orders are often not purchased with a credit card because many retailers and institutions impose restrictions on this transaction method due to the potential for fraud and cash advance policies associated with credit cards. When someone uses a credit card to purchase a money order, the transaction can be viewed as a way to convert credit to cash, which credit card companies may not allow or may treat as a cash advance, incurring higher fees and interest rates.

In contrast, grocery items, online subscriptions, and gift cards are generally accepted forms of payment for credit cards, making them more accessible for purchases. Each of these categories does not pose the same risks or treatment as money orders, allowing consumers to use credit cards without additional complications.