Well... a "build up in blood vessels" is actually called a CLOT. That should help you. :)
Answer:
A. Student A because it requires a hypothesis
I think the scientist distinguish whether an entity is living or non living be describing the single unit of life, the live cell that could multiply, reproduce and generate trough time also through ages. I hope you are satisfied with my answer and feel free to ask for more
Other population of the primary consumer or to what the consmers eat will expand in number