C) The ability to only pay for what you use.
One of the advantages of EC2 Instances is the per second billing concept. This is given in the AWS documentation also With per-second billing, you pay for only what you use. It takes cost of unused minutes and seconds in an hour off of the bill, so you can focus on improving your applications instead of maximizing usage to the hour. Especially, if you manage instances running for irregular periods of time, such as dev/testing, data processing, analytics, batch processing and gaming applications, can benefit.