You have a massive social networking application that is already deployed on the N.Virginia region ( with newly created key pairs ) with around 100 EC2 instances. You want to deploy your application to multiple regions for better availability. You don’t want to handle multiple key pairs and reuse existing key pairs for the N.Virginia region. How will you accomplish this?

Answer options:

A.Key pair is not a region level concept, all the keys are available globally.
B.Use copy key command line API to transfer key to different regions.
C.Using import key-pair feature using AWS web console.
D.Copy AMI of your EC2 machine between regions and start an instance from that AMI.

Answer - C
Key pairs across regions are not possible. In order to use key pairs across regions, you need to import the key pairs in the respective regions.
You need to go to the respective region, and from the EC2 dashboard, click on Import Key pair and choose the relevant key pair.
Option A is incorrect because the key pair is region specific – not global.
Option B is incorrect because keys cannot be copied across different regions. They need to be imported.
Option C is CORRECT because import key pair functionality enables migrating an EC2 instance from one region to another and use the same PEM key. 
Option D is incorrect because PEM keys cannot be copied to another region as part of the AMI.
For more information on bringing your own key pair, please refer to the below URL-
https://aws.amazon.com/blogs/aws/new-amazon-ec2-feature-bring-your-own-keypair/