Correct answer - "EC2 Reserved Instances" : Reserved instances can provide a capacity
reservation, offering additional confidence in your ability to launch the number of instances
you have reserved when you need them. You save money going with Reserved instances vs on demand
especially in a years worth of time.
"EC2 On Demand Instances" - On-Demand instances let you pay for compute capacity by the hour or
second (minimum of 60 seconds) with no long-term commitments. This will cost you much more than
going with Reserved instances
"EC2 Spot Instances" - Spot instances save you alot more money than on demand but they may not
work in your situation because their is interruptions when AWS needs to reclaim these back