Evaluate monolithic, layered and microkernel architectures according to a efficiency. b robustness. c extensibility. d security.

a) efficiency

Explanation:

Monolithic Highly efficient because every component of the operating system can directly communicate with any other by using function calls.

Layered Less efficient because a user request may need to pass through many layers before it is serviced.

Micro-kernel Efficiency is decreased because of inter - process communication.