Host A is transmitting data to host B on a TCP connection. What is the purpose of the ACK
sent by host B?

A.
The ACK is flow control from host B and tells host A to reduce its transmission rate.

B.
The ACK tells the host A that host B wishes to establish a session.

C.
The ACK tells host A the sequence number of the segment that was just received by host

B.
The ACK tells the host A that host B wishes to establish a session.

D.
The ACK tells host A the sequence number of the next segment that host B expects to
see.