The correct option is D compulsory
Section 152 (3) and (4), no person shall be appointed as a director of a company unless he has been allotted the Director Identification Number under section 154 and every person proposed to be appointed as a director by the company in general meeting or otherwise, shall furnish his Director Identification Number and a declaration that he is not disqualified to become a director under this Act. This makes DIN compulsory for appointment of directors.