Correct answer should be B.
On-Demand Instances: These instances allow you to pay for compute capacity by the hour or second, with no long-term commitments. They are suitable for short-term, spiky, or unpredictable workloads that cannot be interrupted. However, they are not the lowest cost option for long-term, predictable workloads.
Spot Instances: This is the correct choice. Spot Instances allow you to bid on spare Amazon EC2 computing capacity. Spot Instances are available at up to a 90% discount compared to On-Demand prices. They are ideal for workloads that are not time-sensitive and can tolerate interruptions. Since the company's ML processing jobs do not need to run at specific times, Spot Instances offer a cost-effective solution for long-term, predictable workloads.