James Watson and Francis Crick
it would be (D) because you cant see an atom without a microscope and a model is a larger model of the actual thing.
DNA, Chromosomes, Nucleus, Cell, Organism
Explanation:
DNA makes up the Chromosomes, which are stored in the nucleus, which is the brain of the cell, and cells make up organisms.
Answer: B. Closed
In a closed circulatory system is the one in which the blood is circulated to all the parts of the body of the organism through vessels of different length and width. In this system the blood is pumped from the heart through blood vessels where it is transported to different organs and cells of the body instead of filling up the body cavity.