Explanation:

- Leaf cuttings: This method involves rooting a part of a leaf. It's not applicable to coconuts as they grow differently.

- Stem cuttings: Propagation through a piece of stem. Not suitable for coconuts as they require seeds for growth.

- Simple layering: Involves bending a branch to the ground and covering it with soil. Not practical for coconut trees due to their structure.

- Seedling: ?? Coconuts grow from seeds. The coconut fruit itself contains the seed which germinates into a new plant.

- Air layering: A technique of rooting branches while attached to the parent plant. Not applicable to coconut trees as they grow from seeds.