According to Graham's law, at a given temperature the ratio of diffusion `r_A/r_B` of gases A and B is given by
(where P and M are pressures and molecular weights of gases A and B respectively)

Options

A. `((P_(A))/(P_(B)))((M_(A))/(M_(B)))^(1//2)`
B. `((M_(A))/(M_(B)))((P_(A))/(P_(B)))^(1//2)`
C. `((P_(A))/(P_(B)))((M_(B))/(M_(A)))^(1//2)`
D. `((M_(A))/(M_(B)))((P_(B))/(P_(A)))^(1//2)`

Explanation

Rate of diffusion is directly proportional to the pressure and inversely propotional to the molar mass of the gas.
Hence,
`(r_(A))/(r_(B))=(P_(A))/(P_(B))((M_(B))/(M_(A)))^(1//2)`