Concept:Lawrence Kohlberg studied moral development by presenting individuals with moral dilemmas and analyzing their reasoning, not just their choices.Explanation:Kohlberg developed his theory by interviewing children and adults using hypothetical stories. His most famous story is the 'Heinz dilemma,' where a man must decide whether to steal a drug to save his dying wife. By asking participants what Heinz should do and why, Kohlberg classified their answers into stages of moral reasoning. He proposed three levels of moral development, each containing two stages, making six stages in total. Option B is incorrect because it says two general levels, but there are three. Option A is wrong because Kohlberg built on Piaget's work. Option D is a claim by Carol Gilligan, not Kohlberg. Thus, the correct statement is that Kohlberg conducted his research using the Heinz dilemma.Answer:Option C: conducted research on children by presenting them with a hypothetical situation - 'Heinz dilemma.'