The most prevalent environmental threat to human populations caused by landfills is the contamination of surface and ground water. So, most modern landfills in the U. S. are designed to protect against hazardous chemicals escaping into the surrounding soil. What technology makes these protection systems possible?

the answer is true when observing or determining population size, a direct observation is use, in which each organism is counted in a population or in an area. one benefit of this measure is that you get the exact population count but it will take a long time to  determine  the  size  of a  population.

answer; microsoft;