Choice "B" is correct. Generally, a promise to keep an offer open for a specified time is unenforceable unless it is made in writing by a merchant (i.e., a merchant's firm offer) or consideration supports the promise, in which case, an option contract is formed. Here, Bob gave his promise to not purchase another computer in exchange for Jen's promise to keep the promise open. Bob was not legally obligated to forgo purchasing another computer, and giving up the right to do so is valid consideration. Thus, the parties created an option contract to keep the offer open. Choice "a" is incorrect. Although an offer generally may be revoked if not accepted "right away," an exception to this rule exists if the offer is an option. The offer here is an option contract because Bob gave consideration to keep it open (his promise to not buy another computer before noon the following day). Choice "d" is incorrect. Bob did give valid consideration to form an option contract. Bob was not legally obligated to forgo purchasing another computer, so giving up the right to do so is valid consideration. Choice "c" is incorrect. Jen's mere promise to keep the offer open did not obligate her to keep the offer open. Without consideration from Bob to form an option contract to keep the offer open, Jen is not legally obligated to keep the offer open. Thus, choice "B" is a more complete answer.