Do you still have to answer this? Stone is insoluble in water, and its specific gravity is greater than that of water, so it naturally sinks when put in. Stones occupy the space of water, and water also occupies the position of air, so that the water surface will rise. When it rises to the bottle mouth, the crow will drink water. As for the second question, the whole volume is 500 cubic centimeters, water accounts for 250, and the rest is the volume of stone, 250 cubic centimeters.