Which header received at the EC2 instance identifies the port used by the client while requesting ELB?

A.
X-Forwarded-Proto

B.
X-Requested-Proto

C.
X-Forwarded-Port

D.
X-Requested-Port

Explanation:
The X-Forwarded-Port request header helps the user identify the port used by the client while sending a request to ELB.
http://docs.aws.amazon.com/ElasticLoadBalancing/latest/DeveloperGuide/TerminologyandKeyConcepts.html