Please provide a brief explanation why, I am particularly interested in number iv and v

but please answer the rest too :) Thanks

operating systems:

Question #6 Which of the following instructions should be privileged? Explain why. (i) Read the system clock, Clear memory, (iii) Reading from user space (iv) Writing to user space (v) Copy from one register to another (vi) Turn off interrupts, and (vii) Switch from user to monitor mode