Final answer:
Organized options markets differ from OTC options markets in regulation, credit risk, and standardized contracts; however, both types of markets operate based on legal contracts, which is not a point of difference.
Step-by-step explanation:
The question asks to identify which aspect is not a difference between organized options markets and over-the-counter (OTC) options markets. While there are several distinctions between these two types of markets, all options listed except for one indicate differences. In organized options markets, such as those represented by futures exchanges, options contracts are standardized in terms of strike prices, expiration dates, and contract sizes; they are also heavily regulated. These measures reduce credit risk as the exchange itself often acts as the counterparty to every trade (clearinghouse function) and guarantees the performance of contracts.
On the contrary, the OTC market for options is generally less regulated and does not provide standardized contract specifications. Each contract in the OTC market is customized between the buyer and seller, which increases the credit risk because there is no centralized body guaranteeing contract performance. The one aspect listed that is not different between the two types of markets is that both use legal contracts to enforce the terms agreed upon by the parties involved. Despite the differences in regulation, standardization, and risk, the fact that both markets operate based on legally binding agreements is a similarity, not a difference.