QUESTION 4 Which four interprocess communication mechanisms can be used solely for the purpose of synchronization, but not for data tansfer? (Check all four.) Shared memory Pthread mutexes Semaphores Signals Monitors Pipes QUESTION 5 In the many-to-many model (user threads bound one or more to kernel threads), which user thread must be bound one-to-one to a kernel thread to optimize the performance of the application? O The thread that is computationally intensive. The thread that executes the main) function. O The thread that executes the GUI main loop. The thread that often synchronizes with other threads