Solution of differential equation $x dy-y dx=0$ represents:

Question

$$(A)\;a\; rectangular\; hyperbola\quad(B)\;parabola\; whose\; vertex \;is\; at \;origin \quad(C)\;straight \;line\; passing\; through \;origin \quad(D)\;a \;circle\; whose\; centre\; is\; at\; origin$$