What were the main sites for mechanic training and other special schools during this period?

The correct choice highlights Kelly Field in Texas and St. Paul, Minnesota as the main sites for mechanic training and other special schools during the specified period. Kelly Field, established in the early 20th century, played a significant role in aviation training and was crucial for the development of mechanics in the aviation field. It specialized in training related to aircraft maintenance and other technical skills necessary for operational readiness.

St. Paul, Minnesota, also served as an important location for various military training programs, contributing to the development of skilled personnel needed in the aviation sector. Together, these sites provided a robust foundation for mechanic training, ensuring that service members were adequately prepared to support air operations.

Other options point to locations that may have had operational significance or training roles in different contexts, but they did not primarily serve as the main training centers for mechanics during the specified period. Thus, the focus on Kelly Field and St. Paul as primary training sites is what solidifies the choice as the correct answer.