The correct option is A De-differentiation
Differentiation is the process by which cells move from a less specialized (such as stem cells) form to a more specialized form having a specific function. Dedifferentiation is the process whereby completely differentiated cells regress to a simpler state (such as stem cells) and gain the capacity to divide again. The process by which a group of once specialized cells (de-differentiated) return to their original specialized state is known as redifferentiation. Regeneration is the process of renewal or restoration of growth to recreate damaged tissues, limbs etc. So, the correct answer is 'dedifferentiation'.