When creating tests a question solution can be added for each question. Solutions can be presented to learner's in result after test completion or during the test if instant feedback setting is enabled..
Adding Question Solution:
Click 'Add Solution' link to add a solution for selected question. This link opens a new window to add solution.
A popup opens to add a sloution - Add the solution and Save then Publish.
Presenting questions solution to learners
Question solution visibility is controlled by 'Result Visibility" Setting:
Please refer to Result visibility and learners flow