Which option is the default pricing model for Amazon EC2 instances?

Explanations:

On-Demand Instances are the default pricing model for Amazon EC2. They allow users to pay for compute capacity by the hour or second with no long-term commitments, making them flexible for variable workloads.

Savings Plans offer a discounted rate in exchange for a commitment to a consistent amount of usage over a one or three-year term. This is not the default model, as it requires pre-commitment rather than pay-as-you-go.

Spot Instances allow users to bid on unused EC2 capacity, which can lead to significant cost savings. However, they are not the default option and can be interrupted if the spot price exceeds the user’s bid.

Reserved Instances provide a significant discount compared to On-Demand pricing in exchange for a commitment to use a specific instance type for a one or three-year term. This is also not the default option, requiring commitment.