When taxiing up to an active runway, you are likely clear of the ILS critical area when short of which sign?

The correct answer is tied to understanding the specific visual cues provided by the signage at an airport that indicates the boundaries of critical areas for Instrument Landing Systems (ILS). When approaching an active runway, it is essential to recognize that maintaining safety and compliance with regulations is paramount, especially concerning areas susceptible to disruption of ILS signals.

The designated point that marks the limit of the ILS critical area is critical for taxiing operations. The critical area is intended to be kept clear during specific conditions, typically when the weather is poor and aircraft are using the ILS for landing. By recognizing the appropriate signage that indicates you are clear of this critical area, you are contributing to safe operations.

In this situation, the mention of "Illustration H" denotes a specific sign indicating the boundary of the ILS critical area. Identifying this sign as the point at which you are certain to be clear of the ILS critical area reinforces your understanding of airport signage and its corresponding implications for safe taxiing procedures.

The other options may represent different signage or cues at the airport that do not directly indicate the boundary of the ILS critical area, making them less relevant for this specific question.