What phraseology is used for holding in the ILS critical area?

The phraseology "Hold short of ILS critical area" is the correct choice for indicating to a pilot that they must stop before entering the designated area surrounding the Instrument Landing System (ILS) equipment. This specific communication is crucial for maintaining the integrity of the ILS signal, which can be disrupted by aircraft or vehicles within this critical area.

The correct phraseology clearly conveys the required action, emphasizing the location (the ILS critical area) and the instruction to hold short, thereby ensuring pilots understand both the necessity of the instruction and the specific area they are to avoid. This precision helps prevent interference with ILS operations and supports the safe management of air traffic, particularly during critical phases of flight such as approach and landing.

The other options do not provide the specificity needed for controlling access to the ILS critical area. For instance, "hold short of the taxiway" lacks reference to the specific ILS equipment, while "enter the ILS critical area" would imply permission to proceed when in fact the intention is to prohibit entry. "Prepare for approach" does not communicate any information regarding the ILS critical area, thus failing to address the critical nature of the instruction effectively.