the correct answer would be b. lower permeability
Factors that determine the rate of stream erosion-
➡️ Rainfall (more rain more erosion). ✔️
➡️water velocity ✔️
➡️shape, size and depth of channel ✔️
➡️stream capacity to transport eroded material, and the nature of the material being transported✔️
➡️Gradient (Steepness or slope) ✔️
➡️Discharge (Amount of water carried at a given time) ✔️
➡️Load (The materials carried by a stream)
Rainfall (more rain more erosion). ✔️
➡️Slope (the steeper the slope the faster the water will flow) ✔️
➡️Geology (if the bedrock is a soft silt it will erode faster than granite).✔️
Firstly they are not membranes and they are villi's which increase the surface area during digestion
The carbon atom has unique properties that allow it to form covalent bonds to as many as four different atoms, making this versatile element ideal to serve as the basic structural component, or “backbone,” of the macromolecules.