Final Answer:
Web browser software programs like Chrome, Firefox, and Internet Explorer are known as User agents. Option D (User agents) is the answer.
Step-by-step explanation:
Web browsers, such as Chrome, Firefox, and Internet Explorer, fall under the category of user agents. User agents are software applications that act on behalf of the user to access and interact with information on the web. They interpret HTML, CSS, and other web technologies to render web pages, enabling users to view and navigate websites.
While search engines index and retrieve information, internet service providers facilitate internet connectivity, and web servers store and serve web content, user agents focus on the end-user experience, providing an interface for users to access and interact with the World Wide Web.
Option D (User agents) is the answer.