What is the limitation of regeneration in humans?

The limitation of regeneration in humans primarily pertains to the capacity for full restoration of tissues and organs after injury. While humans have some regenerative capabilities, particularly in healing wounds where tissue can repair itself and scarring may occur, the process does not fully restore the original structure or function of the tissue.

For instance, while skin can heal from cuts and wounds, the complex architecture of organs such as the liver or heart does not regenerate with the same efficiency or completeness. Instead, these organs may form a scar tissue that lacks the functionality of the original tissue.

The other choices represent biological processes that are either not regenerative in the traditional sense or are more limited in the scope of regeneration. New limb growth is not possible in humans, and rejuvenation of aging cells refers more to cellular repair and maintenance than to regeneration in the full sense. Therefore, while healing of wounds does involve regeneration, it is the case that humans cannot fully restore organs to their original form, illustrating the limitation of regeneration in our biology.