First aid measures for an unconscious scuba diver should always consider _______ and air embolism.

The correct answer emphasizes the critical need to consider drowning in first aid measures for an unconscious scuba diver. When a diver is unconscious, they are at a significant risk of drowning, especially if they are still in the water or if quick rescue measures are not initiated. Drowning occurs when a person cannot breathe due to being submerged in water, which can happen rapidly in the case of an unconscious diver. Immediate action is necessary to ensure the diver's airways are clear, and appropriate rescue techniques are employed, which may include bringing the diver to the surface, performing CPR, or using other life-saving interventions.

While air embolism is also a serious condition that can occur due to rapid ascent and changes in pressure, the direct and immediate threat posed by drowning must be prioritized in first aid scenarios. Therefore, the focus on drowning in this context is vital for effective emergency response. Other options that do not include drowning overlook this immediate risk, which is critical in situations involving unconscious divers.