Individuals suffering from insomnia disorder have difficulty initiating or maintaining sleep. wake up during their sleep cycle with severe nightmares. do not sleep at all. frequently sleepwalk.

have difficulty initiating or maintaining sleep.

Explanation:

Insomnia disorder refers to the difficulty of falling or sustaining sleep, as well as waking up too early or in the middle of the night and struggling to fall asleep again. Thus, people who suffer from primary insomnia do not experience any health problems; while secondary insomnia is related to physical issues like arthritis, pain, depression and substance abuse.

i believe the answer is a