To solve this question, the user needs to know what UDDI stands for and what its purpose is. UDDI stands for Universal Description, Discovery, and Integration, and it is a platform-independent, XML-based registry for businesses to list their web services.

The correct option is:

D. services: UDDI is used for listing what services are available. It allows businesses to publish their web services to a central directory where they can be easily found and accessed by other businesses and applications. By doing so, UDDI enables interoperability and integration between different systems and applications. Option D is the correct answer.

Option A is incorrect because UDDI is not used for listing data.

Option B is incorrect because UDDI is not used for listing control.

Option C is incorrect because UDDI is not used for listing programs.

Therefore, the answer is: D. services.