A distributed port scan operates by:
A.
Blocking access to the scanning clients by the targeted host
B.
Using denial-of-service software against a range of TCP ports
C.
Blocking access to the targeted host by each of the distributed scanning clients
D.
Having multiple computers each scan a small number of ports, then correlating the results
Explanation:
Think of dDoS (distributed Denial of Service) where you use a large number of computers to create simultaneous traffic against a victim in order to shut them down.