10 单选 (4分)内接于半径为R的球的长方体中的体积最大者的体积为 () .-|||-A. dfrac (8sqrt {3)}(9)(R)^3-|||-B. sqrt (2)(R)^3-|||-C. dfrac (1)(9sqrt {3)}(R)^3-|||-D. dfrac (sqrt {3)}(9)(R)^3