Which of the following statements is correct?
(I) Mycoplasma has no cell wall.
(II) Mycoplasma is the smallest living organism.
(III) Mycoplasma cannot survive without O₂.
(IV) Mycoplasma are pathogenic in animals and plants.

The Mycoplasma are organisms that completely lack a cell wall. They are the smallest living cells known and can survive without oxygen. Many mycoplasma  are pathogenic in animals and plants. In plants it causes witches broom in woody plants, little leaf disease of brinjal. In animals it causes pleuropneumonia.