Final answer:
Phineas Barnum and James Bailey first joined to stage The Greatest Show on Earth, which was a popular traveling circus founded in 1871.
Step-by-step explanation:
Phineas Barnum and James Bailey first joined to stage B) The Greatest Show on Earth.
The Greatest Show on Earth was a traveling circus that was founded by P.T. Barnum and James Bailey in 1871. It was known for its elaborate performances and wide variety of acts, and it quickly became one of the most popular and successful circuses in history. The circus featured a diverse lineup of performers, including acrobats, animal trainers, clowns, and more.
The Greatest Show on Earth played a significant role in American entertainment and created a lasting legacy in the circus industry.