Explanation
All the answers are true, but B is the most complete.

An injection attack is where a malicious actor sends commands or other arbitrary data through input and data fields with the intent of having the application or system execute the code as part of its normal processing and queries. This can trick an application into exposing data that is not intended or authorized to be exposed, or it can potentially allow an attacker to gain insight into configurations or security controls. Missing function-level access control exists where an application only checks for authorization during the initial login process and does not further validate with each function call. Cross-site request forgery occurs when an attack forces an authenticated user to send forged requests to an application running under their own access and credentials.
Cross-site scripting occurs when an attacker is able to send untrusted data to a user's browser without going through validation processes.

The best practice is to totally remove any unneeded services and utilities on a system to prevent any chance of compromise or use. If they are just disabled, it is possible for them to be inadvertently started again at any point, or another exploit could be used to start them again. Removing also negates the need to patch and maintain them going forward.

Explanation/Reference:
Explanation:
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.

Explanation/Reference:
Explanation:
The customer does not administer on behalf of the provider. All the rest are possible options.