Final answer:
While Bob promised to keep the offer open for five days, he can revoke the offer at any time unless it's an option contract, under UCC rule for merchants, or promissory estoppel applies.
Step-by-step explanation:
The statement is true as the general rule in contract law is that an offer can be revoked by the offeror at any time before acceptance, unless the offeree has given consideration for the promise to keep the offer open, making it an option contract. Without an option contract, despite Bob's promise to keep the offer open for five days, he can generally revoke it at any time before acceptance. However, there are some exceptions where an offer cannot be revoked, such as when the offer is part of an option contract, firmer offers under the UCC for merchants, or when promissory estoppel applies.
An explanation for why Bob can revoke his offer relates to the principles of contract formation, where an offer and an acceptance must be present. If Bob has not received any consideration for keeping the offer open, he retains the right to withdraw it at any point before it's accepted. The promise alone does not constrain him legally unless it forms an option contract supported by consideration, or falls under the exceptions mentioned above. These aspects of contract law ensure a balance between the offeror's freedom to manage their own affairs and the offeree's interest in the offer.