You have been asked to use a 28 bit subnet mask to segment the following network block: 108.12.5.0. How many usable hosts per sub-net could you create?（）

A.32 networks with 8 hosts
B.62 networks with 2 hosts
C.30 networks with 16 hosts
D.32 networks with 14 hosts

A.The caller sends a challenge to the authenticator.
B.The authenticator sends a challenge to the caller.
C.The caller encrypts the challenge using a secret.
D.The caller sends a success message to the authenticator.
E.The authenticator encrypts the challenge using a secret.