Route-refresh is a BGP feature/capability instead of a distinct BGP message type

Update messages are used to re-advertise routes that have already been acknowledged.References: BGP Operations and Message Types Overview, Juniper Networks Documentation BGP Update Message, Juniper Networks Documentation

I think the correct answer is D : Route-Refresh Messages BGP systems send route-refresh messages to a peer only if they have received the route refresh capability advertisement from the peer. A BGP system must advertise the route refresh capability to its peers using BGP capabilities advertisement if it wants to receive route-refresh messages. This optional message is sent to request dynamic, inbound, BGP route updates from BGP peers or to send outbound route updates to a BGP peer.

I would say the request-message just requests an update. The Updated prefixes will be sent via an update-message, so A should be correct in my opinion

The answer is A. Refresh messages are used to "request" the re-advertisement of routes. Update messages sends updated routing information to all peers if there is a BGP routing change.

It's D: D. refresh The BGP (Border Gateway Protocol) refresh message is used to request the re-advertisement of the IPv4 unicast or multicast routing information that was previously sent by the sender to the receiver and acknowledged using TCP. This message helps in refreshing the routes in case of route table changes or to ensure that the receiver has the latest and most accurate routing information.

ITS should be A for sure

It should be the "update" message