Why was the narrator puzzled at the end of the story?

Choices:
A. There was nobody in their room after hearing a door open.
B. not enough information
C. They had still not fallen asleep after a couple of minutes.
D. Their cat was out of the house when the story concluded.
There was nobody in their room after hearing a door open.
I had something that might have been a little supernatural.
So I was trying to sleep one time, and I sleep under the blankets 99% of the time. I sleep downstairs, so hearing noise is pretty normal. Also, my door doesn’t lock, or even latch the door handle, so you can just push it open.
So I was laying down, maybe at 60% in terms of how close I was to falling asleep, so I just had to lay down for like 5 more minutes.
But there are a lot of noises, and they freak me out even though I just sorta pretend that they’re definitely a cat or my dog or something.
So, I’m already slightly spooked, but I’m ignoring it and going to sleep anyway.
But then, I hear my door open. That isn’t too weird, I do have cats, so even though by this point my fear is intense, I just sorta blow it off and keep trying to sleep.
And then, something that’s never happened in a situation like this, I feel something moving towards me on my bed.
It feels like a cats movements, with light feet making slight reverberations on the bed.
So my fear goes away entirely, and I’m like “Oh okay, it’s just the cat, that’s good.” And I lift my blankets off my head to let my cat under with me, and because the fear seemed to make the atmosphere under there very hot and tense, and then I look at my bed and there’s nothing.
So I just pretend nothing happened and go to sleep, but that still sticks with me and even though it’s kinda underwhelming I still think it was very strange since I wasn’t at the “edge of consciousness” stage of going to sleep, so I feel like the chances I imagined it aren’t too high.