Choose all of the physical variables that help determine the health of a water system

The “ecological footprint” left by a citizen of a developed nation is about four times larger than that left by a citizen of a developing nation. why is this the case?

The law of thermodynamics states that energy can't be created or destroyed. to natural sources of energy on earth are the

Which is an example of a vestigial structure? a: paw of a lionb: wing of a birdc: appendix of a humand: tail of a cat(i think it's a but i'm not sure)