Final answer:
An element is a simple substance that cannot be broken down into any other substances.
Step-by-step explanation:
An element is a simple substance that cannot be broken down into any other substances. It is the most basic form of matter and is composed of only one type of atom.
For example, hydrogen is an element because it consists of only hydrogen atoms. Oxygen is another element because it consists of only oxygen atoms.
Therefore, the correct answer is b) Element.