The correct answer is "phagocytes".
Phagocytes are cells responsible for fighting infection by engulfing and ingesting bacteria and harmful foreign particles. Once phagocytes come in contact with any foreign and dangerous particle, they bind to them and engulf them. This mechanism of action is called phagocytosis.
They are all rock with different size and shapes and are located in different areas possibly in the same areas but they all have there own unique textures from the photographs and 3 of them look like maybe a fossil of some type of when the dinosaurs where still around and the rocks on the top left corner look smooth and are a small type of igneous rocks. That have been soothed over the years.