The correct answer is B, 'Dynamically scale to meet usage demands.' This is because elasticity in cloud computing refers to the ability to automatically adjust resources to match the current demand. This ensures that applications have the necessary resources to perform optimally without incurring unnecessary costs during periods of low demand. The other options do not directly relate to the concept of elasticity and agility in cloud computing. Option A suggests a static approach that does not adapt to changing demands. Option C implies a physical infrastructure which is not the focus of cloud computing. Option D, while beneficial for application design, does not specifically address the elasticity and agility of cloud resources.