Answer:
The correct answer is d) user agent functions
Explanation:
User-Agent is a fundamental part of the web structure and represents an essential role in the content of negotiation. was formulated to develop the capability to address users, creating requests with different clients, depending on capabilities or context. Some of the functions of User-Agents are "Email functions visible to a user, such as facilities for preparing and submitting messages, filing, replying, and forwarding"
