A solution architect is designing a video streaming service including RTMP distribution that provides the paid video content to customers worldwide. 
What is the most optimal solution to secure delivery of the video content to paying customers?

Answer options:

A.Create IAM users for the customer. Create and assign the IAM Role for the customers. Create and assign IAM policy granting access to the content to the IAM role.
B.Use CloudFront with signed URLs.
C.Use CloudFront with signed cookies.
D.Use AWS STS to provide a temporary access token.

Answer: B
Option A is incorrect because IAM is used for the identity and access management of AWS accounts. Creating an IAM role would allow access to services in your AWS account but would not provide signed URL access to your content provided by CloudFront.
Option B is CORRECT because CloudFront signed URLs should be used for securing and limiting access to content in RTMP distribution.
Option C is incorrect because CloudFront signed cookies cannot be used for RTMP distributions, and they can only support the HLS format.
Option D is incorrect because STS is used for providing temporary access to an AWS account or service to an IAM user. In this situation, the content has to be shared with global users.
Reference:
https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/live-streaming.html
https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/private-content-choosing-signed-urls-cookies.html