I meant to say that when nothing is there for CPU to run then OS would schedule a lowest priority idle task until an interrupt occurs. Now, this may be HLT instruction or may not be. It is processor specific. For Intel processors, staying idle traditionally meant running the halt instruction.
So for GATE purpose, it is safe to assume that the address of the instruction after the HALT is pushed onto the stack.
Having said that I'm still not sure if it is correct and that's why I asked this question. I have also put this question on GateOverflow FBgroup.
If I go according to previous year paper answer should be 2018 and we all know that GO answers are 100% correct!