RedBullGaveMeWings.
I suspect that you are reading the question as meaning something like " a sudden increase or decrease in headwind or tailwind" or "The sudden onset of headwind or tailwind". But the question does none of these things.
It simply asks how being in a headwind or tailwind will affect your IAS. What they want you to know is that an aircraft in flight has no way of knowing what the wind is unless of course the wind suddenly changes. In a steady headwind or tail wind, the IAS will be unaffected.
It would of course hav e helped if they had said that the wind was steady.