Plowing is a farming practice, that creates as its name says, contour lines, these lines are characteristic because they are placed perpendicular to the slope, for this reason, they are a method used to prevent erosion and retain water.
With this information in hand, we can see that option A is not correct because the use of plowing is related to soil loss and not to soil richness per se. Option B is not correct either because the use of insecticides is more related to the type of crop and surrounding vegetation cover. Option C in this case is the correct answer, it is used to reduce erosion and sediment pollution because helps retain soil. Finally, option D is not correct because this method is not related to livestock.