Question

The transport layer protocols used for real time multimedia, file transfer, DNS and email respectively are

Answer 1

U D P: Transport layer protocol which is unreliable but fast.

T C P: Transport layer connection oriented protocol which is secure and reliable but comparatively slow.
So for real time multimedia we need fast processing so UDP is suitable for it.
For file transfer we need security so TCP is suitable for file transfer.
DNS always use UDP
For email we need security so uses, TCP.
Option (c) is correct.