Vegetation catches precipitation on its leaves, slowing it down or holding it for a while. This gives the ground more time to absorb the water, so there's less runoff.
The answers are:
a. physical geography
b. human geography
Geography is divided into two main branches, physical geography, and human geography, and after that, they branch out much more and include the other geographical disciplines in them.
Physical geography is mainly concerned with the study of the natural characteristics of the Earth, both the ones on the surface and the once close to the surface.
Human geography is mainly focused on the study of the human race, the background, perceptions, interactions, organizing, human groups, effects on and from the environment etc.
