Answer:
C. The contract is valid unless Jack did not know he was entering into the contract, or lacked the mental capacity to comprehend its nature.
Explanation:
Since the court was not physically present during the signing, the court need to consider the contract at face value. As long as all the signatures there, the contract must be enforced.
The only thing that Jack can do to escape the contract is by proofing to the court that he's drunk to the point of where he became conscious. Probably through recording or by convincing hal or Sophia to vouch for him. This will be the basis for a 'Lacked the mental capacity' defense.