A crystal has a coefficient of linear expansion 12 × 10^-6 /°C in one direction and 244 × 10^-6 /°C in every direction at right angles to it . Then  the coefficient of cubical expansion of crystal is

• A

  $450\times {10}^{-6}{/}^{0}C$

• B

  $500\times {10}^{-6}{/}^0\mathrm{C}$

• C

  $244\times {10}^{-6}{/}^{0}C$

• D

  $36\times {10}^{-6}{/}^{0}C$