If the vertices of a triangle ABC are A(1, 2, 1), B(4, 2, 3) and C(2, 3, 1), then the equation of the median passing through the vertex A, is

$\frac{x-1}{2}=2 y-4=z-1$

$M = \left(\frac{4+2}{2}, \frac{2+3}{2}, \frac{1+3}{2} \right)$

$M = (3, \frac{5}{2}, 2)$

so  $\frac{x-1}{3-1}=\frac{y-2}{\frac{5}{2}-2}=\frac{z-1}{2-1}$

Equation of median = $\frac{x-1}{2}=\frac{y-2}{\frac{1}{2}}=\frac{z-1}{1}$

Option: 4