John needs a ride to the airport and asks his buddy paul to give him a ride. paul says, "okay, but you need to give me a ride to the airport next month when i go to my sister's wedding." as john gets out of the car at the airport, he declares, "i owe you one, mate." when paul asks john for a ride to the airport, john turns him down, explaining that he's got a date. is john's promise legally enforceable?

The correct answer is: No, because no monetary consideration was paid by either party.

When John said he "owes Paul one" and accepts Paul request: "okay, but you need to give me a ride to the airport next month when i go to my sister's wedding.", he is not legally obliged to uphold his promise. This is because there were no formal and written legal contract that stated this, and furthermore, both men did not agree on a monetary consideration if the promise was not upheld. 

Idont know which one is right   but i know that c is wrong and a might be wrong