Side of equilateral triangle = AB = BC = CA = $$\frac{2}{\sqrt{3}}$$ cm
Also, BD = $$\frac{BC}{2}=\frac{1}{\sqrt3}$$ cm
$$\therefore$$ $$AD=\sqrt{AB^2-BD^2}$$
= $$\sqrt{\frac{4}{3}-\frac{1}{3}}$$
= $$\sqrt{\frac{3}{3}}=\sqrt1=1$$ cm
=> Ans - (D)
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