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 function of the car is affected by the pedal that controls the amount of gas the engine gets? Answer: acceleration
[EX A]: The car pedal on the right controls the amount of gas the engine gets. How does this affect the car's acceleration?.

[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: What is defined as force per unit area? Answer: pressure
[EX A]:
Pressure is defined as force per unit area, .