I believe the answer is "un".
I remember taking a test like this, and I am 99% sure that was the right answer. Also, when you say it out loud, it makes more sense (If you have heard a bit of Spanish before).
I hope this helps you! I tried my best :)
Answer:
Unos
Explanation:
Exámenes means exams
So if it’s in plural the article must also be in plural so UNOS it’s the only plural in those options so... unos is the answer
