听力原文： A twenty-three day search operation that begins Thursday will include 84 America

ns and their Vietnamese counterparts split into 8 teams. The spokesman for the operation said four of the teams are currently in the midst of a dry season. The spokesman said Vietnam turned over sixty-seven sets of remains the Vietnamese believed to be of Americans last year, the most since they began returning such remains in the early 1980s. Vietnam first allowed American search teams into the country in 1988, and the first consisted of just 3 men. Vietnam has turned over hundreds of sets of remains since the end of the war in 1975. So far 280 such sets have been positively identified as the remains of missing Americans. The remains are examined by forensic specialists at a US military laboratory in Hawaii. The fates of more than twenty-two hundred American servicemen who are missing in Southeast Asia remain unsolved. Sixteen hundred and forty-eight of those are listed as missing in Vietnam or its waters. In an interview with the Associated Press, Major General Thomas Needham, the search operation commander, said he was pleased with the progress being made to account for the missing men. He said he and his teams were allowed to go wherever they wished in Vietnam. General Needham said that he constantly pushed the Vietnamese to find and hand over' more documents about the missing men. General Needham said he did not believe the Vietnamese government was holding back remains. However, he said some individuals who had come across remains were holding them back in the hope of being paid for them. The US docs not pay for remains. In a related development the US military announced Wednesday that Admiral Charles Larson, the commander in chief of the Pacific, will visit Vietnam beginning January 16. Admiral Larson will visit the American Missing in Action Office in Hanoi, discuss the issue with Vietnamese officials, and travel south to observe the excavations. Admiral Larson will become the highest ranking US military officer to visit Vietnam since the end of the war. Admiral Larson's visit and extensive search come at a time when officials in Washington say the question of the US trade embargo against Vietnam is under active review.

How many missing American servicemen have been positively confirmed dead in Vietnam so far？

A．67.

B．280.

C．84

D．1,648.00