There are 3 boxes numbered $B\left(i=1,2,3\right)$ each having 10 balls also numbered from 1 to 10. Three balls are selected one from each box. If number on ball selected from $B$ box is $n$ such that $n_1<n_2<n_3$ then the number of ways equal to (A) ${.}^{10}{C}_3$ (B) ${.}^{10}{C}_2$ (C) $2{.}^{10}{C}_2$ (D) $2{.}^{10}{C}_3$

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