Question: In an MBMS (Multimedia Broadcast/Multicast Service) context, what is the primary purpose of the <fmt> part in the media description line for RTP (Real-time Transport Protocol)?
Option 1: To specify the transport protocol used for media transmission
Option 2: To indicate the type of media (audio, video, or text)
Option 3: To enumerate one or more payload types used in the RTP session
Option 4: To define the media codec's sampling rate
Explanation: In the context of MBMS and RTP, the <fmt> part is crucial for specifying the payload types utilized within an RTP session. This directly impacts how receivers interpret the media streams, making it essential for successful multimedia broadcast/multicast transmissions. The correct answer, Option 3, highlights this key function. Options 1, 2, and 4 are incorrect because they describe functions associated with other parts of the media description line: <proto> (transport protocol), <media> (type of media), and potential attributes like "a=fmtp" (format parameters such as codec settings), respectively.