What is the purpose of the sequence number of the ESP or AH header?

What is the purpose of the sequence number of the ESP or AH header?

A.
To provide protection from someone trying to modify the packet content

B.
To provide protection someone trying to replay captured data later in the session

C.
To provide protection from missing packetsthat have been encrypted

D.
To provide protection from hackers changing the sequence number in the layer 4header