Answer:
Cancer disease occurs when the abnormalities occurs during cell division of stem cells. Stem cells are those cells which are produced in the body and used by the body when the cells are older or get damaged. When the division of these stem cells are uncontrollable, cancer occurs which spread to the surrounding cells. When a large group of cancer cells grow in size, it turns into tumor.
The oxygen cycle can be found in all but the geosphere. There's oxygen in the atmosphere, so it has to be there, and the biosphere includes living things, which breathe oxygen, and water (hydrosphere) is made up of partly hydrogen, so there has to be oxygen there as well.
