Answer :
The best answer for the question is: C. documented.
So, the sentence will be: It is a documented fact that petting furry animals reduce blood pressure, as there's plenty of evidence to support it.
What is a Documented Fact?
A documented fact is a truth that can be verified from other sources.
So, when the writer says that the fact that petting furry animals reduces blood pressure is documented, it means that it can be verified from other reliable sources of information.
Learn more about documented facts here:
https://brainly.com/question/6807070