Out of 30 observation 10 are $\frac{1}{2}+d,10$ are $\frac{1}{2}$ and other $10$ are $\frac{1}{2}-d$ whose variance is $\frac{4}{3}$ then $\left|d\right|$ is equal to (A) $1$ (B) $\sqrt{2}$ (C) $\sqrt{3}$ (D) $\frac{1}{\sqrt{2}}$

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