The correct option is A one independent director
As per provisions of Section 173(3) of the Companies Act, 2013, the board shall be called by giving not less than seven days‘ notice in writing to every director at his address registered with the company and such notice shall be sent by hand delivery or by post or by electronic means, provided that a meeting of the Board may be called at shorter notice to transact urgent business subject to the condition that at least one independent director, if any, shall be present at the meeting