The correct answer is C. balance between inputs and outputs from the hill slope system.
The form of a hill slope is determined by the balance between the inputs and outputs of the hill slope system. Inputs include precipitation, weathering, and erosion. Outputs include runoff, sediment, and solutes. The balance between these inputs and outputs determines the rate of slope development.
A. Inputs to the hill slope are the factors that add material to the slope, such as precipitation, weathering, and erosion. These factors can cause the slope to become steeper or more eroded.
B. Outputs from the hill slope are the factors that remove material from the slope, such as runoff, sediment, and solutes. These factors can cause the slope to become less steep or more filled in.
D. None of the above is not the correct answer because the form of a hill slope is determined by the balance between inputs and outputs.