When should wing anti-ice be turned on for final taxi?

The correct choice aligns with the operational protocols for wing anti-ice systems, specifically concerning conditions under which these systems should be activated during final taxi. Wing anti-ice should typically be turned on as a precautionary measure, unless Type II or IV anti-ice fluids have been applied to the aircraft.

Type II and IV anti-ice fluids have specific properties designed to prevent ice from forming on the wing surfaces, allowing for prolonged protection in icing conditions. If these fluids are in use, the need for the wing anti-ice system to be engaged is less critical, as the fluids offer adequate protection against ice accumulation. Therefore, in situations where these fluids are applied, the wing anti-ice system is usually not required, thus justifying the guidance that it should not be turned on in such cases.

Conditions listed in the other options do not trigger the requirement for wing anti-ice activation in a manner that overrides this specific guideline about the use of Type II or IV fluids.