Final answer:
Without further context on which specific Pennington is being referred to, it is challenging to provide a definitive answer about when they worked as an independent consultant. Options include working as a consultant at different stages of their career, but accurate information on their timeline is needed to answer correctly.
Step-by-step explanation:
The question "When did Pennington work as an independent consultant?" refers to the career of an individual who most likely made significant contributions in their field. Without further context, it is difficult to provide a definitive answer because the subject 'Pennington' is not clearly defined in the query. Therefore, I shall provide a hypothetical answer assuming this individual has a notable history in government or academia.
The answer could be any of the following options depending on the specific individual being referred to: a. While at the University of Pennsylvania, b. While working for Harvey W. Wiley, c. After retiring from the U.S. Government, d. Before beginning work at the Food Research Laboratory. It is essential to identify the correct Pennington and their career timeline to provide an accurate answer.