Answer:
A. Provide prearrival medical instructions to the caller.
Explanation:
In almost every circumstance that involves a call to 911, the person who's calling will be extremely nervous or desperate, since he/she'll be in search for help. In this case, the EMD has to be fast in order to identify how severe the situation is and take action based on it, while calming down the caller to get the necessary information from him/her. In the case of alarming medical emergencies, prearrival medical instructions provided by the EMD can determine the chances of a person to survive or to die.