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