Explanation
Within IaaS, where the cloud customer is responsible for everything beyond the physical network, the number of users on a system would not be a factor in billing or service charges. The core cloud services for IaaS are based on the memory, storage, and CPU requirements of the cloud customer. Because the cloud customer with IaaS is responsible for its own images and deployments, these components comprise the basis of its cloud provisioning and measured services billing.

Dynamic optimization is the process through which the cloud environment is constantly maintained to ensure resources are available when and where needed, and that physical nodes do not become overloaded or near capacity, while others are underutilized.

Explanation/Reference:
Explanation:
A virtual machine is ultimately an image file residing a file system. Because of this, even when a virtual machine is "powered off," it is still susceptible to attacks and modification. A physical server that is powered off would not be susceptible to attacks.

Explanation
DNSSEC relates to the integrity of DNS resolutions and the prevention of spoofing or redirection, and does not pertain to the actual security of transmissions or the protection of data.

Explanation
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.