Reactants. Reactants are the substances that are needed for a chemical reaction to occur. Without reactants there are no products.
So the similarity of the planets and the dwarf planets are they are both mostly round because they have sufficient gravity to flatten their own surfaces into a sphere. The differences are that planets are big enough to clear the whole region of space where they orbit the sun whereas dwarf planets do not.
B is not part of the cell theory; there are many types of cells that do not have cell walls, so the statement cannot even be generally true.
