Q: Flatworms have a concentration of nerve tissue in the head end, which was a major step in the evolution of what organ?


Read this paragraph and choose the correct option from the provided answers:

Flatworms have a concentration of nerve tissue in the head end. This was a major step in the evolution of a brain. It was also needed for bilateral symmetry.

 Choices:

- liver

- heart

- kidney

- brain


A:
brain