What is the subnet id of a host with an IP address 172.16.66.0/21?

1.	What is the subnet id of a host with an IP address 172.16.66.0/21?
A.	172.16.36.0
B.	172.16.48.0
C.	172.16.64.0
D.	172.16.0.0
Answer» D. 172.16.0.0

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