Final answer:
Option D is true. Franz could revoke his offer to sell the tickets to Joe before it's accepted, even before the deadline he set. The offer can be communicated to be revoked at any time before acceptance, making it the best-fit choice with regard to the law of offer and acceptance in this scenario.
Step-by-step explanation:
In the scenario of Franz offering tickets to Joe, certain principles of the law of offer and acceptance apply. Specifically, option D is true: Franz could revoke the offer at any time before acceptance, even before 10:00 p.m. on December 15. This is because an offer can be revoked by the offeror at any point before it has been accepted, provided that the revocation is communicated to the offeree. Moreover, creating a contract does not necessarily require a written offer, so option E is incorrect. Option A would be true if Franz sold the tickets to someone else before Joe accepts, thus making the original offer to Joe void. Option B is misleading because the mailbox rule, which states that acceptance is effective upon dispatch, only applies under certain jurisdictions and specific conditions. As for option C, once Joe makes a counter-offer, it nullifies the original offer. Therefore, if the counter-offer is rejected, the original offer cannot be accepted unless Franz re-extends it.