The general solution of the differential equation $\frac{{ydx - xdy}}{y} = 0$ is

A. $xy = C$

B. $x = C{y^2}$

C. $y = Cx$

D. $y = C{x^2}$

Option C is correct

The given differential equation is:
$\frac{{ydx - xdy}}{y} = 0$
$\Rightarrow$ $\frac{{ydx - xdy}}{{xy}} = 0$

$\Rightarrow$ $\frac{1}{x}dx - \frac{1}{y}dy = 0$
Integrating both sides,

we get:
$\log |x| - \log |y| = \log k$
$\Rightarrow$ $\log \left| {\frac{x}{y}} \right| = \log k$

$\Rightarrow$ $\frac{x}{y} = k$
$\Rightarrow$ $y = \frac{1}{k}x$
$\Rightarrow$ $y = Cx$ where $C = \frac{1}{k}$

Hence, the correct answer is C.