Which variable is the one that is adjusted by the esperimenter?

Which entry is in the wrong position in the table?

What is point source pollution of an aquatic ecosystem? a) pollution of freshwater sources b) pollution from many sources that combine into one c) pollution that occurs over a wide area; water that runs off from fields, parking lots, and other land surfaces d) pollution that can easily be identified with a single discharge source, such as an open pipe which drains into a body of water

What is the difference in the cell cycle between healthy cells and cancerous cells?