What is the most efficient summarization that R1 can use to advertise its networks to R2?

Refer to the exhibit.

What is the most efficient summarization that R1 can use to advertise its networks to R2?

A.
172.1.0.0/22

B.
172.1.0.0/21

C.
172.1.4.0/22

D.
172.1.4.0/24
172.1.5.0/24
172.1.6.0/24
172.1.7.0/24

E.
172.1.4.0/25
172.1.4.128/25
172.1.5.0/24
172.1.6.0/24
172.1.7.0/24

Explanation:
The 172.1.4.0/22 subnet encompasses all routes from the IP range 172.1.4.0 – 172.1.7.255.