Ms. Sanderson, the science professor wished to conduct an experiment and she gathered her class for that purpose. She held a rock and a piece of wood in her hands and she placed these in a beaker of mysterious liquid.
Astonishingly, the wood sunk but the rock floated.
Ms. Sanderson now turned to the class and asked them, "What is this mysterious liquid in the beaker?"
Please help the class to come up with a valid answer.