Which statement is correct about the sequence number in the IPSec packets?

Which statement is correct about the sequence number in the IPSec packets?

A.
The sequence number is used by default on all ScreenOS devices.

B.
The sequence number is checked by default by the ScreenOS device for every received
packet.

C.
The sequence number is used to provide anti-replay services for ESP and AH packets.

D.
The sequence number is used to uniquely identify every security parameter index in a
tunnel.