The most reliable evidence of a control's effectiveness is a system-generated testing report. A system-generated testing report is a document that shows the results of automated tests performed by the system to verify that the control is functioning as intended and producing the expected outcomes. A system-generated testing report is reliable, because it is objective, consistent, accurate, and timely, and because it can provide a high level of assurance and confidence in the control's effectiveness. The other options are not as reliable as a system-generated testing report, although they may provide some evidence of the control's effectiveness. A risk and control self-assessment, senior management's attestation, and a detailed process walk-through are all examples of manual or subjective evidence, which may be prone to errors, biases, or inconsistencies, and which may provide a lower level of assurance and confidence in the control's effectiveness. References = Risk and Information Systems Control Study Manual, Chapter 3, Section 3.4.1, page 3-32.

Explanation/Reference:
Explanation:
Mitigation is the strategy that provides for the definition and implementation of controls to address the risk described. Here in this scenario, you are trying to reduce the risk of operation failure by guiding administrator to take daily backup, hence it is risk mitigation.
Risk mitigation attempts to reduce the probability of a risk event and its impacts to an acceptable level.
Risk mitigation can utilize various forms of control carefully integrated together. The main control types are:
Managerial(e.g.,policies)

Technical (e.g., tools such as firewalls and intrusion detection systems)

Operational (e.g., procedures, separation of duties)

Preparedness activities

Incorrect Answers:
A: The scenario does not describe risk avoidance. Avoidance is a strategy that provides for not implementing certain activities or processes that would incur risk.
B: The scenario does not describe the sharing of risk. Transference is the strategy that provides for sharing risk with partners or taking insurance coverage.
C: The scenario does not describe risk acceptance, Acceptance is a strategy that provides for formal acknowledgment of the existence of a risk and the monitoring of that risk.