Answer:
B) a voidable contract, one that Jack can void.
Step-by-step explanation:
A voidable contract is valid until one of the parts decides to void it. In this case, if Jack decides to purchase Jennifer's computer and later discovers that she lied about how old it was, he can void the contract and return the computer to get his money back.
What Jennifer is doing is basically lying about the material facts of the product that they are bargaining and it represents a valid reason for voiding the contract.