Final Answer:
The option that would make an advertisement illegal is c. Advertising property the broker owns, is not being sold through the brokerage, yet the licensee states that they are a real estate broker.
Step-by-step explanation:
In the given options, advertising property that the broker owns but is not being sold through the brokerage, while falsely claiming to be a real estate broker, would make an advertisement illegal.
This violates the principle of transparency and honesty in real estate advertising. Such false representation can mislead potential clients and compromise the integrity of the real estate transaction process.
To ensure fair and ethical practices, real estate brokers must accurately represent the properties they advertise and refrain from making false claims about their credentials.
Additionally, advertising a nickname (option a) may not necessarily make the advertisement illegal, as long as it does not involve misleading information.
Using an email without the real estate broker's license number (option b) could be a violation of regulatory requirements, but it may not automatically render the entire advertisement illegal.
Lastly, advertising as a member of the National Association of Realtors (option d) could be problematic if it involves false information, but membership status alone may not be the sole factor in determining the legality of an advertisement.
In conclusion, option c is the most likely scenario that would result in an illegal advertisement, as it involves a combination of false representation and advertising properties not associated with the brokerage.
This underscores the importance of truthfulness and accuracy in real estate advertising to maintain trust within the industry.