Final answer:
In the absence of the flashing green SPEED message during descent at 100-ft radio altitude, the pilot would generally need to perform a manual speed adjustment. The decision should be based on standard operating procedures and training for the specific aircraft.
Step-by-step explanation:
The student's question pertains to a scenario during an aircraft's descent where a specific flight deck message does not display as expected. If the flashing green SPEED message does not display during descent through 100-ft radio altitude, the correct pilot action depends on the context of the situation and the specific operating procedures of the aircraft in question. However, generally, the absence of a speed message at this phase of flight may indicate that the automatic systems are no longer regulating speed, hence the pilot may need to ensure the speed is appropriate by performing a manual speed adjustment. If any abnormal situations arise or if there's any doubt about the safety of the landing, initiating a go-around would be the prudent course of action. This question does not immediately suggest an emergency or a continuation of the descent without addressing the lack of the speed message. It is crucial for the pilot to constantly monitor the situation and adhere to standard operating procedures and training.