Final answer:
The best tool to begin an investigation into the causes of laboratory labeling errors is b. Flow chart.
Step-by-step explanation:
A flow chart is a diagrammatic representation that illustrates the sequence of operations to be performed to arrive at the solution. It enables the investigator to visualize each step in the process, making it easier to pinpoint where errors are occurring. Once errors are located, modifications can be made to correct them. It's an excellent tool for organizing thought processes and identifying potential sources of problems in a sequence of events.
Other tools mentioned, such as a histogram, prioritization matrix, or affinity diagram, serve different purposes. A histogram would show the frequency of errors but not necessarily their causes, a prioritization matrix helps to prioritize solutions based on certain criteria, and an affinity diagram groups large amounts of data based on natural relationships, which could be useful once potential causes are identified for further analysis.