Authentication is the process of proving whether the identity presented by a user is true and valid. This can be done through common mechanisms such as user ID and password combinations or with more secure methods such as multifactor authentication.

KRI stands for key risk indicator. KRIs are the red flags if you will in the world of risk management. When these change, they indicate something is amiss and should be looked at quickly to determine if the change is minor or indicative of something important.

Explanation
Infrastructure as a Service pools the compute resources for platforms and applications to build upon, including CPU, memory, and storage. Applications are not part of an IaaS offering from the cloud provider.

An XML firewall is most commonly deployed in line between the firewall and application server to validate XML code before it reaches the application. An XML firewall is intended to validate XML before it reaches the application. Placing the XML firewall between the presentation and application layers, between the firewall and IPS, or between the application and data layers would not serve the intended purpose.

Measured service is the aspect of cloud computing that pertains to cloud services and resources being billed in a metered way, based only on the level of consumption and duration of the cloud customer. Although they sound similar to the correct answer, none of the other choices is the actual cloud terminology.