It's letter C. When ever you read "breaks down" always think decomposition. When you read that compound get together to form "a single" compound, think synthesis.
Answer:
Iron shavings
Explanation:
A substance that has a fixed chemical composition throughout and a mixture is when two or more substances are combined, but they are not combined chemically.
There are chief differences between organic and inorganic compounds. ... The main difference is in the presence of a carbon atom; organic compounds will contain a carbon atom (and often a hydrogen atom, to form hydrocarbons), while almost all inorganic compounds do not contain either of those two atoms.
