The sentence that could be added to this paragraph as a supporting detail is (C.) chess teaches students to think ahead about the consequences of their actions.
A supporting detail in a paragraph or essay is additional information that is included in order to support the main idea of the text. The supporting detail provided in option C) could be included in this paragraph because, as well as the previous sentences in the paragraph, it is also referring to the positive impact that playing chess has on students. In other words, this supporting detail helps the writer to prove that chess can teach students just as much as any other sport.