In public key cryptography,

A.
The public key is used to encrypt and decrypt.

B.
Only the private key can encrypt and only the public key can decrypt.

C.
If the public key encrypts, then only the private key can decrypt.

D.
Only the public key can encrypt and only the private key can decrypt.

Explanation:
The correct answer is “If the public key encrypts, then only the private key can decrypt”. Answers
“Only the private key can encrypt and only the public key can decrypt” and “Only the public key can
encrypt and only the private key can decrypt” are incorrect because if one key encrypts, the other
can decrypt. Answer “The public key is used to encrypt and decrypt”is incorrect because if the public
key encrypts, it cannot decrypt.