RSA public key.

[Sunil K. Vallamkonda]

Looking at SSH documentation, following
methods of authentication are supported:

                        Password
                         Host-Based Authentication
                         User Public Key Authentication
                         Kerberos Authentication
                         Pluggable Authentication Modules (PAM)
                         SecurID

1) In method: "User Public Key Authentication" - 
  Is RSA public key mechanism used here ?
  If so, it this the primary and only algorithm or are there alternatives
  to RSA here ?

2) In "Password" method above, is password sent in cleartext on wire ?

3) what is RHOSTS_RSA authentication method ?

4) In "Host-Based Authentication" method - Is rhosts method used here ?

Any information/pointers is appreciated.

Thank you,