Final answer:
The acceptable reason to not cooperate with another broker is the other broker's unethical practices. Professional ethics in the real estate industry require brokers to work honestly and in the best interest of their clients, so cooperating with one who acts unethically is unacceptable.
Step-by-step explanation:
The acceptable reason to not cooperate with another broker among the options provided is c) The other broker's unethical practices. Cooperation in the real estate industry is essential for the efficient functioning of the market; however, maintaining ethical standards is paramount. Personal dislike (a) is not a professional reason to refuse to cooperate. The unfamiliarity of the other broker with the market (b) doesn't justify non-cooperation either; all brokers were once unfamiliar and had to learn. Different commission structures (d) should not interfere with the cooperation, as commissions can often be negotiated between brokers to facilitate the transaction.
Real estate professionals are guided by a code of ethics which underlines the necessity to work towards the interest of clients and to treat all parties honestly. Cooperation with a broker who has demonstrated unethical behavior can compromise this commitment and potentially harm clients, involve you in legal predicaments, or tarnish your professional reputation. Thus, ethical concerns provide a substantial and acceptable reason to decline cooperation with a fellow broker.