Alice and Bob are both employees at the same company. They currently participate in an asymmetric cryptosystem and would like to use that system to communicate with each other securely$.$ Before sending the message, Alice would like to apply a digital signature to it$.$ What key should she use to create the digital signature?

A$.$

Alice's private key

B$.$

Bob's private key

C$.$

Alice's public key

D$.$

Bob's public key