A board convened under
section 2106 of this title shall certify that, in the opinion of at least a majority of the members if the board has five members, or in the opinion of at least two-thirds of the members if the board has more than five members, the officers recommended for promotion are the best qualified for promotion to meet the needs of the service (as noted in specific direction furnished the board by the Secretary under
section 2115 of this title) of those officers whose names have been furnished to the board.