Reproduction in Planaria takes place through

The correct option is Fragmentation.

Detailed Explanation:
Planaria is a genus of flatworms famous for their extraordinary regenerative capabilities. Fragmentation is a form of asexual reproduction where the body of an organism breaks into several distinct pieces (fragments), and each piece grows and regenerates the missing parts to develop into a complete new individual.

When a planarian is cut or damaged, specialized stem cells called neoblasts migrate to the site of the wound. These cells proliferate and differentiate into all the various cell types needed to reconstruct the missing structures, enabling each small fragment to grow back into a fully formed flatworm.

Let us examine why the other choices are incorrect:
- Budding: In this process, a new individual develops as an outgrowth or bud from the parent's body (commonly seen in organisms like Hydra and Yeast). Planaria do not reproduce by budding.
- Binary Fission: This is a method where a single-celled organism divides into two equal halves (typical in Amoeba and Bacteria).
- Asexual spores: Spores are microscopic structures adapted for survival and dispersal, commonly used for asexual reproduction in fungi and some plants (like ferns and mosses), but not in multicellular animals like Planaria.