Final answer:
Insomnia is the inability to get to sleep, stay asleep, and/or get a good quality of sleep. It is a common sleep disorder characterized by difficulty falling or staying asleep. The correct option is a.
Step-by-step explanation:
The inability to get to sleep, stay asleep, and/or get a good quality of sleep is called Insomnia. Insomnia is the most common sleep disorder and is characterized by difficulty falling or staying asleep. Individuals with insomnia often experience long delays between going to bed and falling asleep, and may also wake up several times during the night.
The correct option is a.