Question: In MBMS, what standard(s) do the language and (optionally) country tags, used in the SDP attribute "a=lang" for labeling media languages, originate from?
Option 1: ITU-T Recommendations and IETF RFCs
Option 2: ISO 639 for language tags and ISO 3166 for country tags
Option 3: 3GPP TS Specifications and ETSI Standards
Option 4: Unicode Consortium and W3C Guidelines
Explanation: The correct answer is Option 2 because, according to the telecom standards for Multimedia Broadcast/Multicast Service (MBMS), the language tags are derived from ISO 639, while the optional country tags come from ISO 3166. This ensures standardized identification of languages and countries in media labeling within MBMS protocols.