You currently run your infrastructure on Amazon EC2 instances behind an Auto Scaling group. All logs for your application are currently written to ephemeral storage. Recently your company experienced a major bug in the code that made it through testing and was ultimately deployed to your fleet. This bug triggered your Auto Scaling group to scale up and back down before you could successfully retrieve the logs off your server to better assist you in troubleshooting the bug. Which technique should you use to make sure that you can review your logs?

Answer options:

A.Configure the ephemeral policies on your Auto Scaling group to back up on terminate.
B.Configure your Auto Scaling policies to create a snapshot of all ephemeral storage on terminate.
C.Install the CloudWatch Logs Agent on your AMI, and configure CloudWatch Logs Agent to stream your logs.
D.Install the CloudWatch monitoring agent on your AMI, and set up a new SNS alert for CloudWatch metrics that triggers the CloudWatch monitoring agent to backup all logs on the ephemeral drive.

Answer – C
You can use CloudWatch Logs to monitor applications and systems using log data. For example, CloudWatch Logs can track the number of errors that occur in your application logs and send you a notification whenever the rate of errors exceeds a threshold you specify. CloudWatch Logs uses your log data for monitoring; so, no code changes are required. 
Option A and B are invalid because Autoscaling policies are not designed for these purposes.
Option D is invalid because you use Cloudwatch Logs Agent and not the monitoring agent.
For more information on Cloudwatch logs, please refer to the below link:
http://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/WhatIsCloudWatchLogs.html