Which address range efficiently summarizes the routing table of the addresses for router Main?

Refer to the exhibit.

Which address range efficiently summarizes the routing table of the addresses for router Main?

A.
172.16.0.0./21

B.
172.16.0.0./20

C.
172.16.0.0./16

D.
172.16.0.0/18

Explanation:
The 172.16.0.0./20 network is the best option as it includes all networks from 172.16.0.0 –
172.16.16.0 and does it more efficiently than the /16 and /18 subnets. The /21 subnet will not
include all the other subnets in this one single summarized address.