Final Answer:
Sales records are an external data source for an information system.
Step-by-step explanation:
External data sources provide information to an information system from outside the organization. Among the options provided:
a. Transaction reports: Typically generated within the organization based on internal transactions.
b. Labor statistics: May be obtained externally but are often compiled by government agencies.
c. Personnel records: Primarily internal data, containing employee information.
d. Sales records: External data source, as sales data often involves transactions with customers, clients, or external entities.
Sales records provide crucial information about the organization's revenue, customer interactions, and market trends, making them a valuable external data source for an information system.
Option D is the answer.