(3) An employer or a trade union of employers upon whom a claim for recognition has been served shall, within twenty-one days after the service of the claim -
(a) accord recognition; or
(b) if recognition is not accorded, notify the trade union of workmen concerned in writing the grounds for not according recognition; or
(c) apply to the Director General to ascertain whether the workmen in respect of whom recognition is being sought are members of the trade union of workmen concerned and give a written notice of such application to such trade union of workmen.