“For many reasons, humans did not notice they were being watched”
states the central idea of the first paragraph. The correct
answer between all the choices given is the first choice. I am hoping that this
answer has satisfied your query and it will be able to help you in your
endeavor, and if you would like, feel free to ask another question.
Do you mean synonyms to the word dark that are also nouns?
Charcoal and Raven
I think it would go after
a) animation this is a video made up of sever still images played together very fast