Bob's friends invited him to a concert this weekend, but he doesn't have any cash to pay for the tickets. Bob decides to use his credit card and purchase a ticket anyway. In other words, Bob is using $\_\_\_\_\_\_$ to buy the tickets.

$($Select the best answer below.$)$

A$.$

cash

B$.$

debit

C$.$

credit

D$.$

money he has already earned

E$.$

None of the answers are correct.