Answer: Option (b) is the correct answer.
Explanation:
A compound is defined as the substance in which different atoms chemically combine together in a fixed ratio by mass.
For example, [tex]Ca(NO_{3})_{2}[/tex] is a compound as here both calcium ion and nitrate ion chemically combine together.
A compound can be broken down into its constituent particles.
Whereas an atom is the smallest particle present in a substance. It is indivisible in nature.
A molecule is a substance that contains either same or different atoms which are chemically combined together.
For example, [tex]Cl_{2}[/tex], [tex]H_{2}O[/tex] etc are molecules.
An element is a substance that consists of only same type of atoms.
For example, aluminium element will consists of only aluminium atoms.
Thus, we can conclude that compound is the most specific classification of [tex]Ca(NO_{3})_{2}[/tex].
