Theoretically, if you don't consider other factors, "large body size" and "long life" are the two most reasonable answers for animals prone to cancer. Because "large body size" means that there are more cells that make up the body, and "lifespan" "Long" means that more new cells are needed for replacement; the more cells, the higher the chance of random mutations in cell division. If the following items are true, the above arguments can be questioned most by which:. ['Short-lived small animals such as mice are susceptible to cancer.', 'Humans have an increased risk of cancer due to smoking.', 'Long life, large elephants have a low probability of developing cancer.', 'Manatees and hoofs are close relatives, they are very different in size, but they are not susceptible to cancer.']