ANS:D - none of these

The binary diffusivity in gases does not depend upon the pressure. Binary diffusivity (𝐷𝐴𝐵DAB​) is a measure of how readily one gas species diffuses through another gas species. It is defined as the proportionality constant between the molar flux of one component and the concentration gradient of that component in a mixture of gases. Mathematically, it is expressed as: 𝐽𝐴=−𝐷𝐴𝐵𝑑𝐶𝐴𝑑𝑥JA​=−DAB​dxdCA​​ Where:

• 𝐽𝐴JA​ is the molar flux of component A,
• 𝐶𝐴CA​ is the molar concentration of component A,
• 𝑥x is the direction of diffusion,
• 𝐷𝐴𝐵DAB​ is the binary diffusivity of component A in component B.

Binary diffusivity primarily depends on the nature of the components involved, specifically their molecular size, shape, and interaction energies. It is relatively independent of pressure and temperature under normal operating conditions in gases. Therefore, the correct answer is pressure.