Only the narrator knows the thoughts and feelings of one character.
The answer is D. A dialogue involves a <em>exchange of opinions</em>, like a conversation towards a particular subject. <em>Even</em> an <em>inner dialogue</em>, not talking directly to the people, <em>still</em> passes important information that help the audience understand things not so obvious. In sentences A, B and C, phrases like "I told them" and "I said" don't seem to indicate a dialogue. <em>But in D, "I asked them" invites the audience to a conversation.</em>
