This starfish had lost two of its arms. by what process could it regenerate them?

Starfish, actually not being fish but instead marine invertebrates, can amputate its own arms and reproduce is self asexually. The central discs are split into fragments through a process that is called fission, and which the regeneration process happens and genetically identical limbs are thereby reproduced.

This movement is also referred to as  glacial plucking