Cloud services make exclusive use of virtualization, and systems change over time, including the addition, subtraction, and reimaging of virtual machines. It is extremely unlikely that the exact same virtual machines and images used in a previous audit would still be in use or even available for a later audit, making the tracking of changes over time extremely difficult, or even impossible. Elasticity refers to the ability to add and remove resources from a system or service to meet current demand, and although it plays a factor in making the tracking of virtual machines very difficult over time, it is not the best answer in this case.
Resource pooling pertains to a cloud environment sharing a large amount of resources between different customers and services. Portability refers to the ability to move systems or services easily between different cloud providers.

The hypervisor level, as a backend cloud infrastructure component, is not a unit where limits may be applied to control resource utilization. Limits can be placed at the service, virtual machine, and cloud customer levels within a cloud environment.

To monitor data in use, the DLP solution's optimal location would be on the user's client or workstation, where the data would be used or processed, and where it would be most vulnerable to access or exposure. The network perimeter is most appropriate for data in transit, and an application server would serve as middle stage between data at rest and data in use, but is a less correct answer than a user's client. A database server would be an example of a location appropriate for monitoring data at rest.