Operating Systems questions need help

a) What does it mean for a machine instruction to be privileged? For each of the following instructions, state whether it should be privileged or not, and explain why.

b) IN = Input from device port

c) INT = Call to interrupt = software interrupt

d) PUSH = Push data onto user stack

e) HLT = Halt processor https://en.wikipedia.org/wiki/X86_instruction_listings