Explanation:

- Leaves: Papaya plants are not propagated using leaves. The leaves do not have the capability to develop into a new plant.

- Seeds: Papaya is commonly propagated using seeds, making this the widespread technique in commercial cultivation. It’s efficient, economical, and allows for the development of many plants.

- Roots: Generally, papaya is not propagated through roots. The roots of papaya plants aren’t used for propagation purposes.

- Stem: While stem cuttings can propagate some plants, papayas aren’t typically grown this way in commercial practices.

- Fruits: Fruits are the end product of the plant and are not used for propagation. However, they contain seeds that are used for growing new plants.