Explanation

Elasticity in AWS refers to the ability to automatically scale computing resources up or down based on demand. The two correct answers are:

• B: The ability to rightsizing resources as demand shifts - This is a core aspect of elasticity where AWS services can automatically adjust capacity to maintain performance while minimizing costs.

• E: How easily resources can be procured when they are needed - Elasticity enables rapid provisioning of additional resources during demand spikes and de-provisioning when demand decreases.

Why the other options are incorrect:

• A: How quickly an Amazon EC2 instance can be restarted - This relates to instance recovery or availability, not elasticity.
• C: The maximum amount of RAM an Amazon EC2 instance can use - This refers to instance specifications and hardware limitations, not elasticity.
• D: The pay-as-you-go billing model - This describes the AWS pricing model, which complements elasticity but is not elasticity itself.

Elasticity is a fundamental cloud computing concept that allows organizations to match resource allocation with actual demand, providing cost efficiency and performance optimization.