Person A answered: "our sustainable competitive advantage is our high level of IT expenditures (e.g., $100M). Person B answered: "no, our sustainable competitive advantage is our high level of cash holding." Person C answered: "dumb. Our sustainable competitive advantage is our expensive but non-exclusive (i.e., can be purchased) equipment such as machines used to manufacture products." Person D answered: "Our sustainable competitive advantage is our customer loyalty coming from customer satisfaction." Who's right