Refer to the graphic.

What optional EIGRP configurations will be required in order to achieve full connectivity
within AS 100?

A.
Use the EIGRP no auto-summary command on R1 and R2.

B.
Use the EIGRP no auto-summary command on R3 and R4.

C.
Use the passive interface on the R1 and R2 interface that connects to the 10.1.1.0/24 and
10.1.2.0/24 subnet respectively.

D.
Use the passive interface command between the R3 and R1 connection and between the
R3 and R2 connection.

E.
Use the variance command on R3.

Explanation:
EIGRP automatically summarizes routes at the classful boundary, the boundary where the
network address ends as defined by class-based addressing. In most cases, auto
summarization is a good thing, keeping the routing tables as compact as possible
In the presence of discontiguous subnetworks, automatic summarization must be disabled
for routing to work properly. To turn off auto-summarization, use the following command:
Router(config-router)#no auto-summary