A simple subject is probably the most basic unit in sentence construction. A subject is a noun, which is a person, place, thing, or idea. A subject tells us who or what the sentence is going to be about. Without a subject, we cannot have a complete sentence. A simple subject is a subject that has just one noun as the focus of the sentence. This means that only one noun does the action, or connects, to the verb of the sentence.
I just took the test or question thing and B and D are correct.
The correct plural form of echo is echos or echoes. Either way it is grammarly correct. I believe that echoes is the correct form.
echoes
It can be perseverance, courage, maybe even hope.