Final answer:
In Oregon, a broker can transition from representing just one party to becoming a disclosed dual agent as long as both the seller and buyer give their informed consent.
Step-by-step explanation:
In Oregon real estate law, once an agency relationship is established between a broker and a client, it can change under certain circumstances. Specifically, the answer to the question of whether this relationship can change is (a): Yes, the established relationship may be changed to disclosed dual agency if both parties, which are the seller and buyer, agree to let the agent represent them both in an offer to purchase. This situation requires clear disclosure and informed consent from both parties, thereby creating a dual agency scenario where the broker owes fiduciary duties to both the seller and the buyer.