Chemical composition describes? a. the types of atoms that make up a sample of matter b. the arrangement in a sample of matter c. all of the above

The right answer is A.

Since matter is generally composed of several pure bodies (chemical compounds and simple bodies), the chemical composition of a product furnishes the quantity or proportion of each of the pure substances which compose it; they are generically called components.

For answer B it is rather the definition of a chemical structure, it refers to both its molecular topology, its geometry (molecular geometry or space group for a crystal) and its electronic structure.

yes, because even though a theory has a  lot of evidence to support it, it is not always true