Notice that BGP transmits messages over TCP connections. What is a reason that BGP uses TCP to transmit its messages?

What will be an ideal response?

BGP is designed for maintaining paths among different organizations, namely
intranetworking. If there is a failure of the paths in BGP environment and if it takes some time to converge for outer network route, the whole network would be unusable and try to obtain the valid path to communicate with a host outside. This causes severe delay to communication of intranetworking. Because of this characteristic, BGP can take advantages of using TCP by noticing shortage of its neighbor BGP router rapidly. TCP’s connection-
oriented fashion can give fast response of link failure to the other BGP peers.
BGP is an exterior gateway protocol for communication between routers in different autonomous systems. BGP routers send to their neighbors only those routes that have changed. BGP routers do not send periodic routing updates so a reliable connection(TCP) is needed when BGP neighbors exchange full routing information.