Its C. Whenever you perform an experiment you want to make sure its as controled as it can possibly be.
Volume is the space that an object occupies. Mass is the amount of matter in a given object.
Answer:
Animals and plants need to get rid of carbon dioxide gasses through a process called respiration carbon moves from fossil fuels to the atmosphere when fuels are burned the ocean and other bodies of water absord some carbon from the atmosphere the carbon is dissolved into water.
Be there is different germs