Answer: Option (b) is the correct answer.
Step-by-step explanation:
Elements are defined as the substance which contain same type of atoms.
An element cannot be divided into simpler substances by any physical or chemical means.
For example, a piece of aluminium will contain only atoms of aluminium.
The periodic table contains all the elements present in nature.
Thus, we can conclude that out of the given options the statement they can be separated by a chemical reaction, does not describe elements.