What is the layered design of an operating system?

Question $10$ options:

The way the operating system is structured into a series of layers, each of which builds upon the functionality provided by the lower layers.

The way the operating system is structured into a series of layers, each of which provides different levels of security.

The way the operating system is structured into a series of layers, each of which provides a different set of functions for users.

The way the operating system is structured into a series of layers, each of which provides a different set of functions for developers.