Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. Corporate leaders expanded the role of middle managers, who now had the responsibility to introduce systematic techniques of cost-accounting and a carefully designed hierarchy of control. B. Corporate leaders replaced the former hierarchy of control with a new system, the main advantage of which was that it divided responsibilities among middle managers. C. Corporate leaders were transformed into middle managers as a result of innovations such as the systematic division of responsibilities and the introduction of careful cost-accounting procedures. D. Corporate leaders introduced a variety of innovative managerial techniques, the most important probably being the middle manager, a new executive layer below owners.