This question behaviour is just like deferred feedback, but with an additional input box where students can give a reason why they gave the answer they did.

No attempt is made to automatically grade the explanation, nor is it required. However, it may be used in various ways, for example

1. The teacher may want to manually edit the grades where the student gave a wrong answer, to give partial credit if the student used the right method or approach.
   
2. The student might want to explain their thinking, so that later, when the results and feedback are revealed, they are reminded of what they were thinking at the time, and so can reflect more deeply.