I'm taking a test and have to guess the right answer to the question after the article. Article: It was a sunny holiday Monday. Olivier Ferrante was cooking sausages on the barbecue and entertaining friends in his garden north of Paris when the phone rang. The call came from the BEA, France's air accidents investigation bureau , where the 38-year-old former football player and driver was an investigator. The news was grim. "An Airbus is missing over the Atlantic: we need you." As a safety investigator,Ferrante and his teams had participated, directly and indirectly,in the recovery of crashed planes from the Red Sea, the Black Sea,and every ocean. But this investigation would be his toughest ever: the plane had disappeared without a witness, or a trace on radar . At least eight ships and a dozen military aircraft gathered on the plane's last known position, about halfway between Brazil and Western Africa. After six days the aircraft's tail fin and 50 bodies were spotted on the surface and the first burning questions were answered. The plane wreckage and passenger injuries indicated the doomed Airbus was unbroken when it hit the water. It was not exploded apart by a bomb or lightning, now broken up by violent weather. Strangely, no mayday message had been sent by its pilots. Ferrante worked energetically with his team:collecting offers of help from around the world, consulting navy ministries and research organizations in France and elsewhere, and contracting suitable ships and high-tech equipment. He would not return home for another 29 days. His team used the Autonomous Underwater Vehicle(AUV) operated around the clock, searching about 400 square kilometers a day. But the race against time was lost and no signals were heard and no more wreckage was found. Day after day, the screen remained bare except for objects that turned out to be stones or garbage from ships. Stressed by media attention and painful meetings with victims' s,Ferrante went jogging one day to clear his head. Then he had an idea. He decided to look at what had happened to nine other planes that crashed after something abruptly... Question: What made it take so long a time to find the missing Airbus? Options: A: The investigators were not working hard as it was holiday time. B: No mayday message was sent by its pilots before crashing. C: Not enough investigating force was put into the searching work. D: The strategy used in the first stage of the search was not effective.
D