Answer: Option (b) is the correct answer.
Explanation:
A compound is defined as the substance in which different elements are chemically combined together in a fixed ratio by mass.
For example, is a compound and elements are present in 1:4 ratio.
A compound can be divided into its constituent or simpler substances.
On the other hand, a molecule is defined as a specie that contains same type of elements.
For example, is an oxygen molecule.
And, an element is defined as a substance which is made up of only one type of atoms. An element can never be broken down into its constituent particles.
For example, a piece of lithium metal will contain atoms of lithium only.
Thus, we can conclude that the statement elements are made up of one kind of atom best explains how elements can be distinguished from molecules and compounds.