G is the centroid in the equilateral △ ABC. If AB = 1

G is the centroid in the equilateral △ ABC. If AB = 10 cm then length of AG is :

[A] $\frac{20\sqrt{3}}{3}cm$
[B] $10\sqrt{3}cm$
[C] $\frac{10\sqrt{3}}{3}cm$
[D] $5\sqrt{3}cm$