Chemisorption is irreversible.

The substance which is accumulating on any surface can be called as an adsorbate and the surface on which the process of adsorption is going on can be called as adsorbent and this whole process is called as adsorption.

Chemisorption process involves the formation of new chemical bonds at the contact surface of the adsorbate and adsorbent.

The new chemical bonds are either ionic or covalent. Due to the formation of new chemical bonds, we can say that it is an irreversible process.

Hence, the correct answer is option A. True.