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: Stis are diseases caused by what that spread through sexual contact? Answer: pathogens
[EX A]: STIs are diseases caused by pathogens that spread through sexual contact. Abstinence from sexual activity and other risk behaviors is the only completely effective way to prevent the spread of STIs.

[EX Q]: Question: The only obvious difference between boys and girls at birth is what type of organs? Answer: reproductive
[EX A]: The only obvious difference between boys and girls at birth is their reproductive organs. However, even the reproductive organs start out the same in both sexes.

[EX Q]: Question: What kind of organisms are prokaryotes? Answer: single-celled
[EX A]:
All prokaryotes are single-celled organisms.