As a child, you may have dug in the dirt and played around with platyhelminthes: flatworms nematode: roundworms annelida: segmented worms mollusca: mollusks

Option C, Annelida: segmented worms

Explanation:

Annelids are  segmented worms which are prominently found in the soil of park and yards.

Some common examples of annelids are  ragworms, earthworms, and leeches

While Platyhelminthes are predominantly found in moist habitat such as  marine water , freshwater etc,. Nematodes are parasites found in circulatory, respiratory and digestive system and finally the Mollusca are found in water bodies only.

Hence, option C is correct