Which of the following is a primary source related to Walter Wellman?

A primary source is an original document or physical object that was written or created during the time under study, providing direct evidence about the topic. In the case of Walter Wellman, a journalist and explorer known for his attempts at transatlantic flight in the early 20th century, "The Aerial Age" serves as a primary source because it directly relates to his work and experiences in aviation during that specific historical period.

This publication would likely include firsthand accounts, reports of his flights, and insights into the challenges and advancements of aviation during Wellman's life. Such sources are invaluable for understanding the context and significance of Wellman’s contributions to aviation, as they offer an authentic glimpse into his thoughts, endeavors, and the technological landscape of the time.

In contrast, the other options are likely secondary sources that provide interpretations or summaries of aviation history rather than direct evidence or firsthand accounts related to Wellman's specific actions or views. Therefore, "The Aerial Age" is the best choice as a primary source associated with Walter Wellman.