A.(SYN=1,ACK=1,seq=11221,ack=11221)
B.(SYN=0,ACK=0,seq=11221,ack=11221)
C.(SYN=1,ACK=1,seq=11220,ack=11220)
D.(SYN=0,ACK=0,seq=11220,ack=11220)