正解:D
The greatest concern with this situation is that a business-critical application does not currently have any level of fault tolerance and thus has a single point of failure. A single point of failure is a component or element of a system that, if it fails, will cause the entire system to stop functioning. Fault tolerance is the ability of a system to continue operating without interruption or degradation in the event of a failure of one or more of its components or elements. Fault tolerance can be achieved by using techniques such as redundancy, replication, backup, or failover. A business-critical application should have a high level of fault tolerance to ensure its availability, reliability, and continuity. References:
* CISA Review Manual (Digital Version), Chapter 5, Section 5.51
* CISA Online Review Course, Domain 3, Module 3, Lesson 22