A Company Has Implemented AWS WAF and Amazon CloudFront for an Application

A company has implemented AWS WAF and Amazon CloudFront for an application. The application runs on Amazon EC2 instances that are part of an Auto Scaling group. The Auto Scaling group is behind an Application Load Balancer (ALB) . The AWS WAF web ACL uses an AWS Managed Rules rule group and is associated with the CloudFront distribution. CloudFront receives the request from AWS WAF and the uses the ALB as the distribution's origin. During a security review, a security engineer discovers that the infrastructure is susceptible to a large, layer 7 DDoS attack. How can the security engineer improve the security at the edge of the solution to defend against this type of attack?

A) Configure the CloudFront distribution to use the Lambda@Edge feature. Create an AWS Lambda function that imposes a rate limit on CloudFront viewer requests. Block the request if the rate limit is exceeded.
B) Configure the AWS WAF web ACL so that the web ACL has more capacity units to process all AWS WAF rules faster.
C) Configure AWS WAF with a rate-based rule that imposes a rate limit that automatically blocks requests when the rate limit is exceeded.
D) Configure the CloudFront distribution to use AWS WAF as its origin instead of the ALB.