When using public key encryption to secure data being transmitted across a network: 
A、both the key used to encrypt and decrypt the data are public. 
B、the key used to encrypt is private, but the key used to decrypt the data is public. 
C、the key used to encrypt is public, but the key used to decrypt the data is private. 
D、both the key used to encrypt and decrypt the data are private. 
ANSWER: C