A jar contains 200 marbles total. Some are black. If you pull 4 marbles out and 1 is black, how many out of the 200 marbles would you guess are black?

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.

compost can be added to topsoil as a:

pesticide