A TCP/IP-based environment is exposed to the Internet. Which of the following BEST ensures that complete encryption and authentication protocols exist for protecting information while transmitted? 
A、Work is completed in tunnel mode with IP security using the nested services of authentication header (AH) and encapsulating security payload (ESP). 
B、A digital signature with RSA has been implemented. 
C、Digital certificates with RSA are being used. 
D、Work is being completed in TCP services.