The primary purpose of an operating system is:

An operating system (OS) serves as the fundamental software that manages computer hardware and software resources. While options B and D (allowing people to use the computer and making computers easier to use) describe important functions or benefits of an OS, they are secondary to its core purpose. The primary goal of an OS is resource management, ensuring that the CPU, memory, storage, and I/O devices are utilized efficiently and fairly among various applications and users. This efficiency is crucial for system performance and stability. Without an OS optimizing hardware usage, applications would struggle to access resources, leading to significant performance bottlenecks and complex programming challenges. Option C is clearly incorrect. Therefore, making the most efficient use of the computer hardware is the foundational objective that enables all other user-facing functionalities.