You work as a network engineer， do you know an IPsec tunnel is negotiated within the protection of whichtype of tunnel？（）

A.OTP
B.OOB
C.SAFE
D.MARS

A.They use the same key for encryption and decryption of data.
B.They use different keys for decryption but the same key for encryption of data.
C.They use different keys for encryption and decryption of data.
D.They use the same key for decryption but different keys for encryption of data.