Context: Woke up at 3:30 am , could n't get back to sleep . It sucks . Two days ago I was still drowsy and sleeping all the time . I still want to sleep all the time , but it is not happening .

Question: What may be the reason I can not go to sleep ?
Options:
0. I have to work nights ,
1. I have insomnia .
2. I have to study .
3. None of the above choices .
Answer: 1