The ratio of intensities of magnetic field, at distances x and 2x from the centre of a magnet of length 2cm on its axis, will be-

4:1  1:4 8:1 1:8

8:1

$ B = \frac{\mu_0}{4\pi} \frac{2M}{(l^2+x^2)^{3/2}} \approx \frac{\mu_0}{4\pi} \frac{2M}{x^3}$ $ \frac{B_1}{B_2} \approx \frac{x_2^3}{x_1^3} = 8:1$