1) Not pre-emptive. P1 continues execution without being pre-empted.
2) Pre-emptive SJF . P1 executes for 1 second followed by execution of P2 for 4 secs. Then P1 finishes execution followed by P3.
3) Not pre-emptive as each of the processes carries on execution without being pre-empted.
4)Pre-emptive but P2 starts execution even before it has arrived which can't happen in reality.
Hence Option 2 is correct .