Why the explanation is the point
An answer alone teaches you one fact in one phrasing. The examiner will not use that phrasing, and often will not ask that fact — they will ask something adjacent that the same reasoning covers. A quiz without explanations trains recognition of a sentence rather than understanding of a topic.
So each question here carries a short reason, tied back to the material, saying why the answer is right. Reading it after a wrong attempt is where the learning happens; reading it after a correct one confirms you were right for the right reason rather than by luck.
The explanation is also the honest check on the question itself. If the reason does not follow from your material, the question was a bad one, and you can see that immediately rather than memorising something wrong.