Given a scientific question, generate a correct answer to it.

[EX Q]: What is the smallest of the galilean moons?
[EX A]: europa

[EX Q]: Clubmosses are not true mosses, though, because they have what?
[EX A]: vascular tissue

[EX Q]: Shark teeth likely evolved from the jagged scales that cover their skin, called what?
[EX A]:
placoid scales