Answer Happy

Hello, the answers as shown in the image are correct howeverthere is one more answer that is correct and unchecked. Which oneis it? This is for Computer Operating Systems
When is a preemptive CPU scheduler called? When a process switches from the running state to the ready state. When a process performs any system call. When the current process calls exit and terminates. When the time slice of the current process expires. When the current process performs a blocking I/O system call.