Fact 1: Flatworms belong to the phylum Platyhelminthes.

Fact 2: Parasitic flatworms have evolved a close association with their hosts.

Given the two facts above, answer the question "organisms belonging to the phylum Platyhelminthes have evolved a close association with their what" with the following options: 
- ovaries
 - Wasps
 - life
 - plant
 - orchids
 - hosts
 - root system
 - tree host


 

      hosts   