Alice is concemed about the integrity of her emails. Thus, when Alice sends an email to Bob she computes a cryptographically strong message digest and appends it to the email before sending it to Bob. After attending this course, Alice becomes paranoid about security and begins to believe that her original scheme to protect integrity of her emails is not adequate So she now begins to encrypt the message digest with Bob's public key. Choose the correct answer from the following statements (a) An additional layer of protection is gained by Alice. This is because Alice has the guarantee that no body other than Bob can verify the integrity of the email (b) An additional layer of protection is gained by Alice. This is because by virtue of the encryption only Bob can now recreate the original email from the digest and compare it with the received one (c) An additional layer of protection is gained by Alice. This is because if Bob is not able to decrypt the message digest Bob will know right away that the message (email + digest) was corrupted. (d) No additional protection is gained by Alice. This is because confidentiality of message digest in no way contributes to the integrity of messages