Final answer:
Geof's offers were terminated by revocation (option C). In the first scenario, Ilsa made a counteroffer, and in the second scenario, Geof changed his mind before Kiki could respond.
Step-by-step explanation:
The student's question involves the termination of offers in contract law. Specifically, the scenario described involves two offers made by Geof to sell his cars.
The correct answer is c) Revocation. Geof's offers were terminated by revocation, which means that Geof withdrew or canceled his offers. In the first scenario with Ilsa, she made a counteroffer by saying she will pay no more than $15,000. This did not terminate Geof's offer, but it creates a new negotiation point. In the second scenario with Kiki, before Kiki could respond to Geof's offer, Geof changed his mind and revoked his offer.
Therefore, the correct answer is c) Revocation.