Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

[EX Q]: Question: What device is used to stop a current in a circuit? Answer: a switch
[EX A]: Understand current as it passes through a series circuit.

[EX Q]: Question: What do scientists believe are the oldest eukaryotes? Answer: protists
[EX A]: Scientists think that protists are the oldest eukaryotes. They most likely evolved from prokaryotic cells, as explained by the endosymbiotic theory. This theory is well-supported by evidence.

[EX Q]: Question: Fertilization is the union of a sperm and egg, resulting in the formation of what? Answer: a zygote
[EX A]:
Fertilization is the union of a sperm and egg, resulting in the formation of a zygote.