100 ml of O₂ diffuses in 100 minutes, under similar conditions one litre of H₂ diffuses in

Rate of diffusion of oxygen is

$\frac{100}{100}=1$

Rate of diffusion of hydrogen is

$\frac{1000}{\mathrm{t}}$

$\frac{1}{1000/\mathrm{t}}=\sqrt{\frac{2}{32}}$

$t=\frac{1000}{1}\sqrt{\frac{1}{16}}$

t=250 min

Therefore the required option is B