Which Amazon EC2 pricing model adjusts based on supply and demand of EC2 instances?

Which Amazon EC2 pricing model adjusts based on supply and demand of EC2 instances?
A . On-Demand Instances
B . Reserved Instances
C . Spot Instances
D . Convertible Reserved Instances

Answer: C

Explanation:

In the new model, the Spot prices are more predictable, updated less frequently, and are determined by supply and demand for Amazon EC2 spare capacity, not bid prices.

Reference: https://aws.amazon.com/blogs/compute/new-amazon-ec2-spot-pricing/