A total of 30 percent of the geese included in a certain migration study were male. If some of the geese migrated during

Total male = 30%
Female = 100 - 30 = 70%
From total geese migrated, 20% were made; female = 100 - 20 = 80%
Migration rate for geese of a certain GMAT = (no. of geese of that GMAT migrating) / (total number of geese of that GMAT)
$$Migration\ rate\ for\ male=\frac{0.2}{0.3}\ \frac{\left(from\ 20\%\right)}{\left(from\ 30\%\right)}$$
$$Migration\ rate\ for\ female=\frac{0.8}{0.7}\ \frac{\left(from\ 80\%\right)}{\left(from\ 70\%\right)}$$
$$Ratio\ of\ migration\ rate=\frac{\frac{0.2}{0.3}}{\frac{0.8}{0.7}}$$
$$=\frac{0.2}{0.3}\cdot\frac{0.7}{0.8}$$
$$=\frac{0.14}{0.24}=\frac{0.07\cdot100}{0.12\cdot100}=\frac{7}{12}$$

Answer = option B