Answer:
The correct answer is letter "C": A listing agreement can be modified, but only if all parties agree in writing.
Step-by-step explanation:
A Listing Agreement is a contract by which the owner of an asset hires a broker so the specialist will be in charge of selling the asset. Listing Agreements are typically used in real estate but can be applied in some other fields. For it to be changed, all the parties involved must agree in the new terms of the contract.