Riparian zones are important to the natural environment because they
a. contain pollution from runoff
b. reduce soil erosion
c. support diverse organisms
d. all of the above

d. all of the above

A riparian zone is the interface zone between the land and a river. The plants near the banks of the river forms the riparian vegetation. This vegetation consists of hydrophilic plants. This area contains pollution from the runoff because the vegetation restricts the flow of pollutants in the water. It reduces soil erosion as the plants are holding the soil which does not dispense in the river water. This zone supports the growth of diversity of plants and animals which are terrestrial and amphibians (which requires both land and water habitats for their survival).  

that is wrong, its not thymus.