Which instance purchasing option meets these requirements MOST cost-effectively?

Explanations:

Dedicated hosts are typically more expensive because they reserve physical servers for exclusive use, making them less cost-effective for a stable, long-term workload.

Reserved Instances offer significant discounts (up to 75%) compared to On-Demand pricing when committing to a one-year term, making them the most cost-effective option.

On-Demand Instances provide flexibility but at a higher cost compared to Reserved Instances, especially for a stable workload running continuously for a year.

Spot Instances are less reliable due to the possibility of being terminated when the market price exceeds the maximum bid, making them unsuitable for stable production workloads.