I would go with A. Money.
Hope that helps you. =)
Competition because they are fighting over a limited resource.
Answer:
A. movement of molecules across a semipermeable membrane against a concentration gradient with a protein
<span>The correct answer here is A. In a scientific experiment, the dependent variable is the variable that is being tested and then measured. The answer referenced in D, the variable that is manipulated, is referring to the independent variable.</span>