Let xᵢ (1 ≤ i ≤ 10) be ten observations of a random variable X. If Σ 10 i = 1 ( xᵢ - p) = 3 and Σ 10 i = 1 ( xᵢ - p)² = 9 where 0 ≠ p ∈ R, then the standard deviation of these observations is
a. 7/10
b. 9/10
c. √3/5
d. 4/5