In a dangerous explosive situation involving solid rocket propellant, responders should first:

In a situation involving solid rocket propellant where there is a potential for an explosive hazard, the most important action is to prioritize safety by ceasing any firefighting operations and evacuating the area. This measure is crucial because solid rocket propellant can combust or detonate under certain conditions, which can pose severe risks to responders and nearby civilians. Calling in a specialized Explosive Ordnance Disposal (EOD) team is necessary since they are specifically trained to deal with explosive materials and can assess the situation more effectively while managing the risks associated with the explosives.

Monitoring the situation tends to keep individuals in proximity to a dangerous environment, which is not advisable during a volatile incident. Attempting to secure the materials may inadvertently trigger an explosion due to movement or disturbances. Assessing and trying to control the fire without proper expertise can also lead to life-threatening incidents.

Therefore, the correct approach emphasizes safety through evacuation and expert involvement, ensuring that professionals are equipped to handle such hazardous situations without jeopardizing lives.