I would have to say skin or hair
Answer:
igneous rocks - geosphere
oceans, frozen lakes - hydrosphere
gaseous nitrogen - atmosphere
sea animals, marine plants - biosphere
Explanation:
The kidneys.
The kidneys keep blood isotonic by removing excess salt and water through urine.
Make sure you are eye level with the meniscus of the liquid level, and measure to the bottom of the meniscus.
