Pls I need help with this taxonomic key. I have been posting this for hours and I'm super stuck pls help

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

Which ideas did your answer contain? check all that apply. no food for organisms no oxygen in the atmosphere no trees or flowering plants no products based on trees or plants (building materials, medicines, fuels, fibers) no fossil fuels

The negative change found inside the plasma membrane is created by potassium ions sodium ions hydrogen ions chlorine ions