Question

Platyhelminthes exhibit cephalization. Which tissue is affected during this process?

Answer 1

I don't even know what Platyhelminthes are, but your answer is right in the question.
'cephalization' What tissue do you think that involves? Notice the root word, cephal-, which means the head

Answer 2

Aside from the root word aspect, do you know what cephalization is?

It's the evolutionary trend that the control of body mechanisms are becoming more concentrated towards the superior anterior portions of several mechanisms, even from the embryo. This formed the 'head' and nervous tissue.