Answer: Option (a) is the correct answer.
Explanation:
When electrons are removed from a neutral atom or ion then the atom attains a positive charge. Therefore, it is called a cation.
For example, [tex]Na^{+}[/tex] is a cation.
Whereas when electrons are added to a neutral atom or ion the then the atom attains a negative charge. Therefore, it is called an anion.
For example, [tex]Cl^{-}[/tex] is an anion.
Anode is a positively charged electrode and cathode is a negatively charged electrode.
Thus, we can conclude that a negatively charged atom or group of atoms is called an anion.