Using public-key (asymmetric) encryption, a sender wants to ensure that only the intended recipient can read a confidential message. Which key should the sender use to encrypt it?

Correct answer: B) The recipient's public key

Explanation

With asymmetric encryption, a message encrypted with the recipient's public key can only be decrypted with the recipient's private key, which only the recipient holds. Encrypting with the sender's private key creates a digital signature that proves origin but does not provide confidentiality.