Low dissolved oxygen is a severe problem in the streams in watershed I because of the inability of light to penetrate the forest canopy.
This is defined as any surface area from which runoff resulting from rainfall is collected and drained through a common point.
Watershed I has the forest which has tall trees which form canopies as its highest land use. Due to the inability of light to penetrate, there is a reduction in photosynthetic activity by plants and reduction in oxygen produced which is why option D was chosen.
Read more about watershed here https://brainly.com/question/1166879