Final answer:
Labor unions are considered external influencers in an organization according to Mintzberg, as they can affect the firm's practices from outside the internal structure. option d.
Step-by-step explanation:
According to Henry Mintzberg, an internationally renowned academic and author on business and management, the external influencers of an organization are those that impact it from outside. None of the options given (CEO and top executives, Middle management, Support staff only, Labor unions) are precisely Mintzberg's external influencers, as the CEOs, top executives, middle management, and support staff are part of the internal governance structure of an organization. However, among the options provided, labor unions are considered external influencers as they can influence the organization's practices, policies, and productivity from outside the firm's internal structure. They play a role in negotiation on wages, benefits, and working conditions for their members.