Rico sends a message to Lola. However, based on how the message was sent, Lola cannot verify it was sent from Rico, but she can verify it has not been altered. What could Rico have done that would have enabled Lola to verify the sender$?$ Select two.

a$.$ Use her public key to encrypt the message instead of her private key.

b$.$ Use his public key to encrypt the message instead of his private key.

c$.$ Generate a digital signature and attach it to the message.

d$.$ Generate a digest and encrypt it with his digltal signature.

e$.$ Generate a digest and encrypt it with his private key.