Answer:
B. Reduce substantive procedures in areas where the internal control was found to be effective.
Step-by-step explanation:
The entire quality of accounting is based on the internal controls design and implementing the internal controls.
If it is assessed that the internal controls are effective and that the company is even implementing it properly and thus, are applied properly, provides certain assurance towards the accounting practice.
As here the auditor has assessed that the internal controls are effectively implemented the evaluation of such areas while auditing will not involve substantive procedures in that area.
This is a positive effect of such internal controls.