When using publickey authentication for SSH users, which descriptions are correct in terms of configuration keys?

When using publickey authentication for SSH users, which descriptions are correct in terms of configuration keys?
A . Need to configure the client’s RSA host private key on the server side
B . The client is required to specify the RSA private key corresponding to the host public key for the SSH user
C . You can use copy and paste to configure the client’s host public key to the server
D . The host private key of the client cannot be configured to the server by copy and paste

Answer: BC