How does the cell membrane of a tube worm maintains a stable environment

The cell membrane of a tubeworm is selectively permeable and they prevent minerals in the water from flowing it in the cell of tube worms. By doing this the cell membrane protects the cell from any osmotic damage. By selectively preventing these minerals it maintains the stable environment in the cell

the answer is:

carbon dioxide

the correct answer, according to e2020, is the second choice there is an occluded front in region a and a cold front in region b.