Answer:
d. Determine whether fixing the first problem caused the second problem.
Explanation:
When verifying functionality you check if the original problem has been resolved and you also need to make sure everything else works. You need to confirm if the users can use all other resources. For example, the user did not report their inability to use the printer because they were so concerned about the original issue. Your solution may have caused another unforeseen problem to occur. Just make sure that everything is working correctly, and the user can perform their duties before you declare the problem resolved.