Forthe ten observations X1, X2, ......, X10 it is given that $$\sum_{i = 1}^{10} x_i = 12$$ and $$\sum_{i = 1}^{10} x_i^2 = 18$$ Then the standard deviation of the data is:

A

$$\frac{5}{3}$$

B

$$\frac{2}{5}$$

C

$$\frac{3}{5}$$

D

$$\frac{5}{2}$$