Groundwater
exists above the earth's surface
is impossible to pollute
forms when precipitation seeps into the soil
is not a usable water source for humans

Ecosystems involve living organisms interacting with non-living things in a productive way; how is photosynthesis an example of this? answer, i will give brainiest to first person to get it right.

Which of these serves as a reference for comparison during a scientific investigation? a)outcome variable (dependent variable) b) test variable (independent variable) c)control group d)hypothesis

How can antibodies "remember" a particular bacterial invader or "antigen" on that invader?