Available choices:
* trichina;
* spore;
* cocklebur;
* cephalization;
Given those answer options, answer the question: Answer the following question given this paragraph: Most flatworms have a distinct head region that includes nerve cells and sensory organs, such as eyespots. The development of a head region, called cephalization , evolved at the same time as bilateral symmetry in animals. This process does not occur in cnidarians, which evolved prior to flatworms and have radial symmetry. Q: The development of a head region is called what? A:
A:
cephalization