Which of the following is a definition of an obligation? Provide answer and explanation

A. a legal requirement to keep a promise.

B. a legal or juridical relationship between a creditor and a debtor, whereby the latter is obligated to fulfill a promise that the former may demand of him.

C. an obligation of an obligor to fulfill an obligee's claim, which, if unfulfilled, is enforceable in court.

D. all of the above.