Final answer:
An asymmetric algorithm key is indicated by using a public key/private key combination for encryption and decryption.
Step-by-step explanation:
An asymmetric algorithm key is indicated by option A) A public key/private key combination used for encryption and decryption. In an asymmetric encryption system, two different keys are used: a public key for encryption and a private key for decryption. The sender uses the recipient's public key to encrypt the message, and the recipient uses their private key to decrypt it.