Sam Promises His Uncle,Bob,that He Will Lose 10 Pounds and Exercise

Sam promises his uncle,Bob,that he will lose 10 pounds and exercise every day during the spring semester in exchange for having his tuition paid for the fall semester.The uncle agrees; but after Sam has lost 10 pounds and exercised all semester,Bob refuses to pay saying that no contract existed.Which of the following is true?

A) Consideration was present, there was an enforceable contract, and Bob has wrongfully refused to pay.
B) There was no consideration present, and Bob has no obligation to pay.
C) There was no consideration present, but Bob must pay under principles of promissory estoppels.
D) There was consideration present, but Bob is not required to pay because the contract was illusory.
E) There was consideration present, but Bob is not required to pay because Bob did not receive a benefit personally.