Which of the following CPU scheduling algorithms is optimal for minimizing average waiting time but requires knowledge of future process execution times? 

Shortest Job First (SJF) scheduling algorithm is designed to minimize the average waiting time by selecting the process with the smallest execution time next. However, it requires knowledge of the future burst times of processes, which makes it difficult to implement in practice. In real-world scenarios, an approximation or estimation of the process's burst time is used. SJF is considered an optimal scheduling algorithm in terms of reducing the overall average waiting time of processes. Option A (First-Come, First-Served) is incorrect because FCFS processes jobs in the order they arrive, which can lead to longer waiting times, especially if a long job arrives first (convoy effect). Option B (Round Robin) is incorrect because Round Robin is fair but does not optimize for minimum waiting time; it assigns fixed time slices to each process, making it suitable for time-sharing systems. Option D (Priority Scheduling) is incorrect because it schedules processes based on priority, not burst time, and may lead to starvation of low-priority processes. Option E (Multilevel Queue Scheduling) is incorrect because it divides processes into different queues based on priority or process type, without optimizing specifically for waiting time.