Explanation:

- Ponds: These are usually natural, though they can be artificially created. However, the typical reference here is to natural ecosystems where aquatic life thrives.

- Forests: Forests are predominantly a natural ecosystem that supports diverse flora and fauna without human intervention.

- Lakes: Similar to ponds, lakes are primarily natural. They serve as a habitat for many species, forming balanced ecosystems usually found naturally.

- Gardens: ?? Gardens are correct. They are artificial ecosystems created and maintained by humans for aesthetics, food, and habitat modification.