Imagine a sponge soaked full of water. No room for air, right? Same with the saturated zone! It's underground soil completely filled with water, leaving no space for air to breathe The correct answer is: b) It's completely filled with water.
The saturated zone is the layer of soil or rock below the surface where all the spaces between particles are completely filled with water. This means there's no room left for air! Think of it like a sponge soaked in water – there's no room for air pockets.
Here's why the other options are incorrect:
a) The pressure is too high: While pressure can affect air movement, it's not the main reason why the saturated zone lacks air. The key factor is that the spaces are already occupied by water.
c) The temperature is too low: Temperature can affect air solubility, but not to the point of completely eliminating it from the soil. Even in cold environments, some air remains trapped in the spaces between soil particles.
d) The soil is compacted: Compacted soil can indeed reduce the amount of air space, but it doesn't necessarily eliminate it completely. The saturated zone refers specifically to the zone where all the spaces are filled with water, regardless of compaction.
In summary, the lack of air in the saturated zone is simply because all the available space is already taken up by water. It's like a full glass – there's no room for anything else!