Answer: Mild Anxiety
Explanation: Anxiety is a certain feeling of restlessness, unease, worries etc. It could be mild or severe, the seriousness or level of this feelings can term it to either be severe or just mild.
The student was able to study for his upcoming examination without distractions, this shows that the anxiety level of the student was mild, it was just a little bit of worries but was put under control and the student didn't allow it run his life.
