Which statement or statements about callback Remote Procedure Call $($RPC$)$ are correct?

The client must have a callback handler to handle the received response

The client must listen for the notification from remote call.

The server must build a thread pool to dispatch a worker thread for each received client request.

The server must send the response to the client where the client callback handler is listening.

The server cannot initiate a callback RPC to the client.

$1,2$

$1,2,3$

$1,2,4$

$1,2,4,5$