An experiment was designed to determine whether or not ultraviolet light affected the growth of lichens. two groups of lichens were grown under identical conditions, in visible light, except one group of lichens was also exposed to uv light while the other was not. in this experiment the group of lichens grown in visible light without uv light is known as the a. control. b. hypothesis. c. dependent variable. d. limiting factor.

The correct answer is option A, that is, control.

A controlled variable refers to something, which is maintained constant all through the experiment. However, in various experiments, one must also require a control. This is distinct from a controlled variable. A control is something, which is used as a standard of comparison for examining the results of an experiment.  

increase soil erosion                                             reduce soil erosion

cattle grazing                                                         hydroseeding

deforestation                                                         contour plowing

                                                                                planting vegetation

plant roots basically hold the top soil

together and stop soil erosion because

in such situation top soil is not removed

during flood but cattle grazing causes

soil erosion because cattle consume the

grasses and herbs and top soil is exposed.

same situation occurs because of

deforestation, the trees and plants are cut

down to expose top soil which causes soil

erosion