How Does The Distinction Between Kernel Mode And User Mode Function As A Rudimentary Form Of Protection (security) System?

Which of the following instructions should be privileged?

  A. Set value of timer.
  B. Read the clock.
  C. Clear memory.
  D. Issue a trap instruction.
  E. Turn off interrupts.
  F. Modify entries in device-status table.
  G. Switch from user to ker