Sometimes nightmares happen because of what happened on the day before you went to sleep, you might’ve been stressed, you watched a horror movie, or you might have been really scared of something, nightmares also happen because you thought about a lot of creepy things or things that would frighten you before you fell asleep.
I am going with the second one. It may be wrong but I have a feeling it's the second one.
Because of water movement in and out of cells
Answer:
Arterial
Explanation:
Please give me brainliest;)