In an informational article, the thesis statement must be supported by facts, details and explanations related to the thesis.
All paragraphs of the article should explain and support the thesis since that is what will give the text unity and what will increase the reader's interest and motivate him/her to keep reading. Since facts can be verified, they can help strengthen the thesis statement. Statistics and explanations can also be used in order for the thesis to make sense to the reader.
In an informational article, what supports a thesis statement are facts, details and expalnations related to the thesis. These are the only reliable sources since, the other options (General information from sources like Wikipedia, Personal experience of the author or the opinion of a non-expert) are not trustworthy.
The causal relationships among plot events in ancient Greek tragedy stem from the belief that nothing happens by chance. Everything that happens is already predetermined, and there is nothing you can do to change it - they didn't believe in chance, but in destiny.