Final answer:
Cecil B. DeMille was associated with Paramount Pictures throughout his directorial career, contributing to the early American cinema landscape.
Step-by-step explanation:
The studio for which Cecil B. DeMille worked during his entire directorial career was c) Paramount Pictures. While film industries around the world were developing and experimenting with various styles and themes, Hollywood was becoming the epicenter of the movie business.
DeMille is known for his epic films and was a leading figure in the American cinema. Although many studios were producing films at that time, DeMille's association with Paramount Pictures was a significant part of his career and the history of early American cinema.