B) assertive communication
True. Lactic acid is caused by strenuous exercise. The lactic acid is formed because while working out, you don't receive as much oxygen.
An author's credentials can determine a health source's credibility. None of the other options would apply to credibility. When it comes to health, if you want to make sure that what you are researching or reading is authentic and reliable you need to find out whether the author is a professional health expert or not. You can do this by finding out their credentials.
