Question

1. what is a main characteristic of platyhelminths?

they have a segmented body plan.
they are flat - bodied organisms.
they are round - bodied.
they have a rigid exoskeleton.

Explanation:

Platyhelminthes, also known as flatworms, are characterized by their flat - bodied structure. Segmented body plans are more typical of annelids. Round - bodied organisms are often nematodes. A rigid exoskeleton is not a feature of Platyhelminthes.

Answer:

They are flat - bodied organisms.