The best explanation for evaluating the credibility of the source would be: "Quabilah should not use this source because it is a blog and eating only once a day does not sound healthy."
This response highlights the importance of critically assessing the validity of health claims and recognizes that just because a source is popular or presents itself as knowledgeable, it does not guarantee accurate or healthy advice. It is essential to consider the credibility of health recommendations based on scientific evidence rather than popularity or the author's profession alone.