The median of first 10 prime numbers is

First 10 prime numbers are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29.

n = 10 (even)

$\operatorname{Median}=\frac{\left(\frac{n}{2}\right)^{\text {th }} \operatorname{term}+\left(\frac{n}{2}+1\right)^{\text {th }} \text { term }}{2}$

$=\frac{5^{\text {th }} \text { term }+6^{\text {th }} \text { term }}{2}$

$=\frac{11+13}{2}$

$=\frac{24}{2}$

$=12$

Hence, the correct option is (b).