Final answer:
Greg, the marketing manager, is fulfilling the role of a Monitor by actively seeking information about competition and industry trends to inform his organization's strategies.
Step-by-step explanation:
Greg, the marketing manager, is engaging in behavior that corresponds to the role of a Monitor. As a Monitor, a manager is tasked with seeking and acquiring work-related information from both external and internal sources. This role involves analyzing the market, understanding competitors, and staying aware of industry trends. In contrast, a Liaison builds alliances and networks, a Disseminator shares information within the organization, and a Spokesperson represents the company externally.