What is the process called when an animal can regenerate a body part?

The process by which an animal can regenerate a body part is known as regeneration. This biological phenomenon allows certain organisms to regrow lost or damaged tissues, organs, or even entire limbs. Regeneration occurs in various species, with notable examples found in starfish, axolotls, and salamanders, which can recover limbs, tails, or other body parts due to specialized cells that can dedifferentiate and proliferate into new tissues.

In the context of the other choices, fragmentation refers to a method of asexual reproduction where an organism breaks into parts, and each part can grow into a new individual, but it does not specifically denote the regenerative capability of restoring a lost part. Fission is another form of asexual reproduction where an organism divides into two or more separate entities, which again does not pertain to the regenerative process. Reproduction is a broader term that encompasses various methods of producing offspring, including sexual and asexual means but does not specifically identify the capability of regrowing lost body parts.

Understanding these distinctions reinforces why "regeneration" is the correct term for the ability of animals to replace lost body structures.