An organization needs a plan to store a large number of files.

Answer options:

A.Ensure that you have RDS set up as an asynchronous Multi-AZ deployment, which automatically provisions and maintains an asynchronous “standby” replica in a different Availability Zone.
B.Set up a number of smaller instances in a different region, which all have Auto Scaling and Elastic Load Balancing enabled. If there is a network outage, these instances will auto scale up. As long as spot instances are used and the instances are small, this should remain a cost-effective solution.
C.S3 should be considered due to the low cost of S3 storage. Enable cross-region replication for the S3 buckets.
D.Set up pre-configured servers using Amazon Machine Images. Use an Elastic IP and Route 53 to quickly switch over to your new infrastructure if there are any problems when you run your health checks.

Answer - C
Option A is incorrect because it can help maintain data, but is not low on cost and is a high-cost option since you need to maintain a Multi-AZ environment. Hence we need to count this option out.
Option B is incorrect because it does not talk about data loss avoidance and is more of network avoidance.
Option C is CORRECT because S3 provides a durable, highly available, low-cost, and more secure storage solution.
Option D is incorrect because it talks about AMIs, but not about the underlying data on EBS storage which will need to be backed up.
More information about Amazon S3:
Amazon S3 is storage for the Internet. It’s a simple storage service that offers software developers a highly scalable, reliable, and low-latency data storage infrastructure at very low costs.
http://docs.aws.amazon.com/AmazonS3/latest/dev/Welcome.html