Which key chain is being used for authentication of EIGRP adjacency between R4 and R2?

You have been asked to evaluate how EIGRP is functioning in a customer network.

Which key chain is being used for authentication of EIGRP adjacency between R4 and R2?

A.
CISCO

B.
EIGRP

C.
key

D.
MD5

Explanation:
R4 and R2 configs are as shown below:

Clearly we see the actual key chain is named CISCO.