Oliver, a student, is preparing to take an exam. He is stressed about the exam and is unable to fall asleep. Even if he falls asleep, he often wakes up during the night or wakes up too early. In this scenario, which of the following disorders is the cause of Oliver's condition?
A. somniloquy
B. somnambulism
C. insomnia
D. narcolepsy

Insomnia

Explanation:

Insomnia is a sleeping disorder in which a person having trouble falling asleep or having trouble staying asleep. This condition varies according to the patient's condition. It can be for a long time or short periods. It is a chronic condition. It occurs three nights a week.  

Insomnia is many types  

Primary insomnia

Secondary insomnia

Insomnia have may reason to occur. Thus here Oliver is suffering from insomnia because of exam stress.

the answer is a. or c.