If a small drop of tiny particles such as pollen grains are dropped into a drop of water on a microscope slide, they will appear to vibrate and spread out. The primary reason for this is a. Currents in the water are pushing them around. b. They have internal energy and that is causing them to move. c. They are being continually struck by randomly moving water molecules from all sides and those strikes fluctuate and are sometimes uneven. d. Internal forces between the particles cause them to repel and attract.