The best evidence of an effective risk treatment plan is that the risk tolerance threshold is above the asset residual risk, because this means that the risk treatment plan has reduced the risk to a level that is acceptable to the enterprise. The risk tolerance threshold is the maximum amount of risk that the enterprise is willing to accept for a given asset or process. The asset residual risk is the remaining risk after applying the risk treatment plan. The risk treatment plan is effective if the asset residual risk is lower than or equal to the risk tolerance threshold. The other options are not the best evidence, although they may also be indicators of an effective risk treatment plan. The inherent risk being below the asset residual risk, the remediation cost being below the asset business value, and the remediation being completed within the asset recovery time objective (RTO) are examples of desirable or expected outcomes of the risk treatment plan, but they do not directly measure the effectiveness of the risk treatment plan. References = CRISC: Certified in Risk & Information Systems Control Sample Questions