What is the maximum tailwind permissible for a CAT II approach?

The maximum tailwind permissible for a CAT II (Category II) approach is indeed 10 knots. This limit is set to ensure that aircraft can safely land under specific low visibility conditions that CAT II approaches involve.

When using an instrument landing system (ILS) for a CAT II approach, pilots rely on precise instruments and guidance to navigate safely to the runway. A tailwind can impact the aircraft's landing distance since it reduces the rate of descent and increases the ground speed upon touchdown. Therefore, the stricter limit of 10 knots helps mitigate risks associated with potential landing overruns and enhances safety during these types of low-visibility operations.

Other options present higher permissible tailwind limits, but these would not align with the safety measurements that ensure effective operation during CAT II ILS approaches. By keeping the maximum tailwind at 10 knots, aviation regulations prioritize safety and operational effectiveness. This is why the correct answer is the 10-knot limit.