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 is produced when hydrogen gas and oxygen gas are ignited? Answer: water
[EX A]: Hydrogen gas and oxygen gas are ignited to produce water.

[EX Q]: Question: Like mammals and birds, and unlike other reptiles, crocodiles have how many chambers in their heart? Answer: four
[EX A]: Like mammals and birds, and unlike other reptiles, crocodiles have a four-chambered heart. But, unlike mammals, blood with and without oxygen can be mixed.

[EX Q]: Question: What spreads sti during sexual contact? Answer: pathogens
[EX A]:
STIs are diseases caused by pathogens that spread through sexual contact.