Answer : 4. "दोनों (b) एवं (c)"
Explanation :

The main function of the operating system is to control both the hardware and software components of a computer. It acts as an intermediary, managing hardware resources and allowing software applications to run and interact with the computer's hardware. While organizing files and folders is a task performed by the operating system, its primary role is to facilitate communication between software and hardware, ensuring the computer functions properly.