Figure shows variation of modulus of magnification m(produced by a thin convex lens) and distance v of image from pole of the lens. Which of the following statements are correct?

 $\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$
$1-\frac{v}{u}=\frac{v}{f}\mathrm{..............}\left(i\right)$ 
Since m is positive in the given figure, therefore m represents magnitude of the magnification. In fact, if a real image is formed by a convex lens, then the image and object will be on opposite sides of the lens. It means, if v is positive, then u will be negative. Therefore,
 $m=-\frac{v}{u}$
Hence, equation (i) becomes
 $m=\frac{v}{f}-\mathrm{1.............}\left(ii\right)$
It means, the graph between m and v will be a straight line having intercept -1 on m-axis and slope of the line $\tan \theta$   is equal to (1/f). hence, options (b) and ( c) are correct. Putting m = 0 in equation (ii),   v = f. Hence, (a) is also correct. Obviously, (d) is wrong.