The contractile vacuole expels excess fluid from the cell.
The answer is tissue fluid. Tissue fluid holds far smaller quantity of protein molecules because they are too large to escape easily over the tiny holes in the capillary endothelium. Tissue fluid doesn't contain red blood cells because they are too large, but does comprise some white blood cells.
Stationary fronts occur when warm and cold air meet. This brings cloudy, and wet weather. So your answer would be C.