The diagrams illustrate how rain is affected when it falls on an area of forested land both before and after houses are constructed. Before houses are built, rainfall is $100\%$, with transpiration at $40\%$, surface runoff at $10\%$ and groundwater at $50\%$. After houses are built, rainfall is $100\%$, transpiration at $25\%$, groundwater at $32\%$ and surface runoff $?\%$. What is the difference in the percentage of surface runoff before and after the houses are built?
- Aincreases by $33\%$
- Bincreases by $43\%$
- Cdecreases to $43\%$
- Ddecreases to $33\%$