Trail, dark (but they is a pronoun.)
A plural noun is a word that indicates that there is more than one person, animal place, thing, or idea. When you talk about more than one of anything, you're using plural nouns. When you write about more than one of anything, you usually use the same word, simply adding an s, es, or ies to the end.
Even though I wasn't there, I did hear about it. As far as I knew, the student was in trouble because she didn't ask the teacher or someone for permission.