While implementing the policy keys in AWS Direct Connect, if you use _____ and the request
comes from an Amazon EC2 instance, the instance’s public IP address is evaluated to determine
if access is allowed.

A.
aws:SecureTransport

B.
aws:EpochIP

C.
aws:SourceIp

D.
aws:CurrentTime

Explanation:
While implementing the policy keys in Amazon RDS, if you use aws:SourceIp and the request
comes from an Amazon EC2 instance, the instance’s public IP address is evaluated to determine
if access is allowed.

http://docs.aws.amazon.com/directconnect/latest/UserGuide/using_iam.html