Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

[EX Q]: Protists are thought to be the oldest eukaryotes.
[EX A]: What is thought to be the oldest eukaryotes?

[EX Q]: Volvox sphere has a distinct front and back end.
[EX A]: What has a distinct front and back end?

[EX Q]: Epithelial cells are found in skin body organ.
[EX A]:
Epithelial cells are found in what body organ?