Which EC2 purchasing option will meet these requirements MOST cost-effectively?

Explanations:

Reserved Instances are designed for long-term commitments and provide a lower hourly rate than On-Demand Instances, but they require a commitment for a 1- or 3-year term. Since the application only runs for 2 months each year, this option may not be the most cost-effective.

Dedicated Hosts are physical servers dedicated to your use, which provide more control over instance placement and compliance. However, they are generally more expensive and are suited for applications that require dedicated hardware rather than short-term usage.

Spot Instances allow you to bid on unused EC2 capacity and can be significantly cheaper than On-Demand Instances. However, they can be interrupted by AWS when the capacity is needed, which makes them unsuitable for applications that cannot afford downtime.

On-Demand Instances allow you to pay for compute capacity by the hour or second without long-term commitments. This flexibility is ideal for an application that runs only for 2 months each year and needs to avoid downtime, making it the most cost-effective option in this scenario.