An e-commerce company wants to lower costs on its nightly jobs that aggregate the current day’s sales and store the results in Amazon S3. The jobs are currently run using multiple on-demand instances and the jobs take just under 2 hours to complete. If a job fails for any reason, it needs to be restarted from the beginning.
What method is the MOST cost effective based on these requirements?

A. Use a mixture of On-Demand and Spot Instances for job execution.
B. Submit a request for a Spot block to be used for job execution.
C. Purchase Reserved Instances to be used for job execution.
D. Submit a request for a one-time Spot Instance for job execution.