The discussion technique that Daniel most clearly shows in this dialogue is (A.) challenging established ideas.
Daniel's use of this technique is a result of his critical reading of the article. Reading critically not only involves getting a basic grasp of the text but it also involves analyzing, evaluating and questioning the information that is being presented. Daniel is not a 'passive reader'. He has read the text in a deep way, which has allowed him to identify the presence of biased information and build his viewpoint about the topic. The dialogue shows that he does not accept the information presented in a passive way: he questions and challenges established ideas instead.