Producer–consumer problem can be solved using:

The Producer-Consumer problem is a classic synchronization challenge where multiple threads must coordinate access to a shared buffer. This requires mechanisms that handle mutual exclusion and process synchronization effectively.\nSemaphores are a foundational tool used to solve this problem by controlling access to the buffer through counting and binary semaphores. Monitors provide a higher-level abstraction that encapsulates shared data and synchronization logic, offering another robust method to prevent race conditions. Event counters can also be utilized in specific implementations to track state changes between producers and consumers.\nSince Semaphores, Monitors, and event counters are all valid synchronization primitives capable of addressing the coordination needs of this problem, Option D is correct. Selecting only one mechanism would ignore other standard solutions taught in operating systems theory.