Which two types of publications must include a registered landscape architect's certificate number?

The correct answer pertains to the requirements for specific types of publications where a registered landscape architect's certificate number must be included. This regulation is in place to ensure that consumers can verify the credentials and professional legitimacy of the landscape architect providing services or expertise within those publication mediums.

In the context of the identifying publication types, radio as a medium is subject to such regulatory requirements because it is a direct form of communication that can influence the public's perception of landscape architectural services. Having the certificate number specifically included allows listeners to verify the qualifications of the professional, thus upholding accountability and trust within the industry.

Other types of publications such as newspapers, websites, and telephone directories typically have broader formats and circulation, where inclusion of such information is less standardized or may not be as readily enforceable. Hence, they do not carry the same regulatory requirement for the landscape architect's certificate number as radio does. This distinction highlights the importance of professional accountability and transparency in more direct communication methods like radio broadcasts.