Question: In an MBMS using FLUTE, which attribute is mandatory for the FLUTE sender to carry in the FDT at the File level, but not supported by the FLUTE receiver due to its inherent nature?
Option 1: Content-Location
Option 2: Transfer-Length
Option 3: Content-MD5
Option 4: mbms2007:Cache-Control
Explanation: Transfer-Length is the correct answer because, according to specifications, it is mandatory in a general context but shall not be carried in the FDT sent by the FLUTE sender, highlighting its unique status as both mandatory (broadly) and not supported (within the FDT context).