Explanation
Resource pooling serves as the biggest challenge to using DLP solutions to protect data at rest because data is spread across large systems, which are also shared by many different clients. With the data always moving and being distributed, additional challenges for protection are created versus a physical and isolated storage system. Portability is the ability to easily move between different cloud providers, and interoperability is focused on the ability to reuse components or services. Reversibility pertains to the ability of a cloud customer to easily and completely remove their data and services from a cloud provider.

Explanation
Regulated PII data carries legal and jurisdictional requirements, along with official penalties for its misuse or disclosure, which can be either civil or criminal in nature. Legal and protected are similar terms, but neither is the correct answer in this case. Contractual requirements can carry financial or contractual impacts for the improper use or disclosure of PII data, but not legal or criminal penalties that are officially enforced.

Explanation
The physical security of crypto keys is of some concern, but guards or vaults are not always necessary.
Two-person integrity might be a good practice for protecting keys. The best answer to this question is option A, because it is always true, whereas the remaining options depend on circumstances.

Interoperability is ability to easily move between cloud providers, by either moving or reusing components and services. This can pertain to any cloud deployment model, and it gives organizations the ability to constantly evaluate costs and services as well as move their business to another cloud provider as needed or desired.
Portability relates to the wholesale moving of services from one cloud provider to another, not necessarily the reuse of components or services for other purposes. Although resiliency is not an official concept within cloud computing, it certainly would be found throughout other topics such as elasticity, auto-scaling, and resource pooling. Scalability pertains to changing resource allocations to a service to meet current demand, either upward or downward in scope.