What mechanism does asymmetric cryptography use to secure data?

A.
a public/private key pair

B.
shared secret keys

C.
an RSA nonce

D.
an MD5 hash

Explanation:
BD
Public key cryptography, or asymmetric cryptography, is any cryptographic system that uses pairs of keys:
public keys which may be disseminated widely, and private keys which are known only to the owner. This
accomplishes two functions: authentication, which is when the public key is used to verify that a holder of the
paired private key sent the message, and encryption, whereby only the holder of the paired private key can
decrypt the message encrypted with the public key.
Source: https://en.wikipedia.org/wiki/Public-key_cryptography