ANS:B - temperature

The gaseous diffusion coefficient generally increases with an increase in temperature. This is because at higher temperatures, gas molecules have greater kinetic energy and move more rapidly, which enhances their diffusion through a medium. However, the effect of pressure on the gaseous diffusion coefficient can vary depending on the specific conditions and the gases involved. In general, for ideal gases, the diffusion coefficient is not significantly affected by pressure changes. However, for real gases and under certain conditions (such as high pressures or when the gas approaches its critical point), the diffusion coefficient may be influenced by pressure. So, the correct answer is: b) temperature