What is a kernel and user space, and how does a system call transition from user to kernel mode?

• A. User space runs unprivileged processes; system calls trap into the kernel, execution occurs in kernel mode, then returns to user space.
• B. Kernel space runs unprivileged processes; system calls execute in user mode.
• C. System calls bypass the kernel and run in user space.
• D. User space runs privileged code; kernel always runs in user mode.

Answer: (A)