Which of these questions could best you evaluate the advice from this website selling supplements? a)which supplements does the author recommend? b)how much do the supplements cost? c)what are the authors credentials? d)how should i exercise according to this author?

The correct answer is C.

If you are on a website selling supplements that are claiming to have a certain type of result, the most important thing you need to do is check the credentials of the author of the advice. You need to know that the information they are telling you is backed up by scientific research and it's not just come nonsense aimed at selling you a product. The author needs to be from a professional health background with proper recognised and accredited qualifications in order for you to know that what you are reading about the product is reliable.