The internal auditor is the best suited to provide objective input when updating residual risk to reflect the results of control effectiveness. The internal auditor is an independent and impartial function that evaluates the adequacy and effectiveness of the internal controls and reports on the findings and recommendations. The internal auditor can provide an unbiased and reliable assessment of the residual risk, which is the risk that remains after the controls are applied. The other options are not as objective as the internal auditor, as they may have vested interests orconflicts of interest in the control environment. References = Risk and Information Systems Control Study Manual, Chapter 2: IT Risk Assessment, Section 2.4: IT Risk Response, page 87.