Two particles start moving simultaneously from the same point and execute simple harmonic motion along the same line. Distances of the particle from their equilibrium position are ${\mathrm{x}}_1=4\cos 4\mathrm{\pi t}\mathrm{cm}\mathrm{and}{\mathrm{x}}_2=4\cos \left(4\mathrm{\pi t}+\raisebox{1ex}{$\mathrm{\pi }$}\!\left/ \!\raisebox{-1ex}{$3$}\right.\right)\mathrm{cm}$. Then maximum separation between the particles is 

• A

  $2\sqrt{3}\mathrm{cm}$

• B

  $4 \mathrm{cm}$

• C

  $3 \mathrm{cm}$

• D

  $3\sqrt{3}\mathrm{cm}$