The correct answer is A.
This letters describes the reaction to American soldiers entering the Dachau concentration camp after its liberation in 1945.
This letter was written on May 7th 1945 by Private First Class Harold Porter. It was written to his parents in Michigan and it describes in details the horrors seen there by the American soldiers. Porter served as a medic with the 116th Evacuation Hospital and he wrote this letter on stationery he found in the office of the camp commandant. This letter is now archived at the Eisenhower Presidential Library.
Before 1945 and facing the defeat, the Nazis transported thousands of prisoners from different concentration camps to Dachau. The resulting overcrowding led to an increase in the death rate ( 200 per day ). There was no way of disposing of the bodies of the dead prisoners who were just left lying around. Due to appalling living conditions, many prisoners died from rapidly spreading untreated tuberculosis and typhus.
The American soldiers were totally unprepared to register the huge number of all the sick or dead bodies there. Porter's letter is thus very upsetting and despairing. The author describes the Nazi atrocities in a very 'unsparing and graphic' manner, making his experience there extremely vivid. He fears he will never forget what he had seen there.