In Amazon AWS, which of the following statements is true of key pairs?

In Amazon AWS, which of the following statements is true of key pairs?
A . Key pairs are used only for Amazon SDKs.
B . Key pairs are used only for Amazon EC2 and Amazon CloudFront.
C . Key pairs are used only for Elastic Load Balancing and AWS IA
E . Key pairs are used for all Amazon services.

Answer: B

Explanation:

Key pairs consist of a public and private key, where you use the private key to create a digital signature, and then AWS uses the corresponding public key to validate the signature. Key pairs are used only for Amazon EC2 and Amazon CloudFront.

Reference: http://docs.aws.amazon.com/general/latest/gr/aws-sec-cred-types.html