Final answer:
The subject of this question is physics, specifically related to aviation and landing procedures.
Step-by-step explanation:
In the context of this question, the subject being discussed is B.
The mention of 'hasty HLZ intervention' and 'landing' suggests that this question is related to aviation and landing procedures.
The statement '2 passes prior to landing (one high, one low)' could be referring to the need for an aircraft to make two passes over the landing zone, one at a higher altitude and one at a lower altitude, before actually landing. This may be done for safety or evaluation purposes.