The Commission may grant six classes of such certificates as are mentioned in Section 58-23-40 after application therefor has been made in writing by the owner of the vehicles upon blanks provided by the Commission and after such hearing as the Commission may deem proper. To the granting of any certificate the Commission shall hear any objections which may be filed thereto with the Commission by any person or corporation who may be affected by any such grant. The six classes of certificates shall be respectively designated certificate A, certificate B, certificate C, certificate D, certificate E and certificate F.