You are part of the IT team of an insurance company. You have 4 M5.large EC2 instances used to compute some data of your core services. The amount of usage of these instances has been very consistent. So you predict that it will not increase in the next two or three years. However, your CFO is asking if there is a way to reduce costs in the EC2 instances. The only requirement will be to be able to change the size of the instances. What do you suggest to get the maximum cost reduction?

Answer options:

A.Purchase a Compute Saving plan.
B.Purchase an EC2 instance saving plan.
C.Purchase a Convertible Reserved Instance.
D.Purchase a Dedicated Instance.

Answer: B
Option A is incorrect because Compute Saving plans also offer flexibility, but the maximum cost reduction is 66%. 
Option B is CORRECT because, with an EC2 saving plan, you can save up to 72% (just like Standard RIs). This plan applies to all of your EC2 instances using the same instance family.
Option C is incorrect because Compute Savings Plans, which provides savings up to 66% (just like Convertible RIs), automatically reduce your cost on any EC2 instance usage regardless of region, instance family, size, OS, tenancy, and even on AWS Fargate or AWS Lambda.
Option D is incorrect because Dedicated Instances are Amazon EC2 instances that run in a virtual private cloud (VPC) on hardware that`s dedicated to a single customer. They cannot reduce the costs.
References:
https://aws.amazon.com/savingsplans/faq/