Tiny pollen grains suspended in water are examined using a microscope. They are observed to keep moving in an irregular and constant way. What causes this random motion?
- AThe grains are moved by randomly moving water molecules.
- BThe grains are moved by random convection currents in the water.
- CThe grains are moved by random rays of light reflecting off them.
- DThe grains are moved by the random motion of their own atoms.