A User Has Setup Auto Scaling with ELB on the EC2

Multiple Choice

A user has setup Auto Scaling with ELB on the EC2 instances. The user wants to configure that whenever the CPU utilization is below 10%, Auto Scaling should remove one instance. How can the user configure this?

A) The user can get an email using SNS when the CPU utilization is less than 10%. The user can use the desired capacity of Auto Scaling to remove the instance
B) Use CloudWatch to monitor the data and Auto Scaling to remove the instances using scheduled actions
C) Configure CloudWatch to send a notification to Auto Scaling Launch configuration when the CPU utilization is less than 10% and configure the Auto Scaling policy to remove the instance
D) Configure CloudWatch to send a notification to the Auto Scaling group when the CPU Utilization is less than 10% and configure the Auto Scaling policy to remove the instance