Answer: C)Sleep deprivation
Explanation: Sleep deprivation is the situation that occurs due to the less sleep an individual gets than the requirement. They are in the tendency of remaining awake and feeling alerted. most of the time. The symptoms of sleep deprivation is irritability ,forgetfulness, not able to concentrate, depressed mood, inability to learn new concepts.
Therefore doctor must have seen these symptoms in Helle and thus suspected of the sleep deprivation.