Looking at the answer options:

1. Time of the anti-icing/de-icing application --> CORRECT. This time is essential information for the calculation of the holdover time.

2. Airport location and elevation --> INCORRECT. The location and elevation of the airport is not relevant. If an aircraft requires de-icing / anti-icing then the weather conditions are critical, whether the aircraft is in Paris, Oslo, Moscow etc. The elevation may contribute to the conditions, but is not information that needs to be taken into account by the personnel.

3. Aircraft type specific procedures --> CORRECT. Although hold over times are not type specific, the procedures for de-icing and anti-icing will vary from type to type.

4. Competence of the de-icing staff --> INCORRECT. According to feedback, there is no option for this question that includes this answer with answers 1 and 3 as well. The regulations do cover the need for ground staff to be trained but does not mention the term competent. Possible wordplay from the examiner. Please contact us if you see a variation on this question.

ICAO Doc 9640
Chapter 5. Holdover Times

5.1 Holdover time (HOT) is the estimated time the anti-icing fluid will prevent the formation of ice and frost and the accumulation of snow on the protected (treated) surfaces of an aeroplane. (…)

5.6 The holdover time begins with the start of the final de-icing/anti-icing application and ends after an elapsed time equal to the appropriate holdover time chosen by the pilot-in-command.

=> Therefore, the time of application of anti-icing/de-icing fluid is important.

Chapter 13. Training of Personnel

13.2 Both initial and recurrent training for flight crews and ground crews are to be conducted to ensure that all such crews obtain and retain a thorough knowledge of ground de-icing/anti-icing policies and procedures, including new procedures and lessons learned.

=> A description of the de-icing and anti-icing policy and procedures for aircraft on the ground is compulsory. Ground crew must be adequately trained to perform these procedures.