Why would access to the user-agent header field of an HTTP request be important for a JSP?

Why would access to the user-agent header field of an HTTP request be important for a JSP?

A.
It allows descriptive information about the device accessing the JSP to be obtained in order to
avoid device-specific limitations.

B.
It provides a secure mechanism to store a user’s username and password for safe and easy
access during Web-based transactions.

C.
It allows for form-based input to be passed within the header rather than in a query string.

D.
It allows conversational state to be managed by the JSP container by maintaining the session
ID of a user.