The first ten indivisible numbers are 2, 3, 5, 7, 11, 13, 17, 19, 29, 29

∴ Required average 

$$\begin{gathered} =\frac{2+3+5+7+11+13+17+19+23+29}{10} \\ =\frac{129}{10}=12.9 \end{gathered}$$

Hence, Option B  is correct.