Answer: Longer distance for the gases to diffuse.
Explanation:
Diffusion can be defined as the movement of particles from a place where its concentration is high to the place where its concentration is very low.
The movement of the particles is dependent on many factors such as solubility of the gases, if the place of concentration is steeper and greater surface area for the gaseous exchange.
The factor which will decrease the rate of diffusion is when the distance between the two place where diffusion will take place is more or large.
Hence, the correct answer is option A
