Final answer:
Julia's father-in-law first saw a concentration camp victim as a dead person, which is highlighted by the experiences of Allied soldiers during the liberation of Nazi death camps in World War II.
Step-by-step explanation:
The first dead person Julia's father-in-law ever saw was d) A concentration camp victim. This is based on the historical context provided which references the atrocities witnessed by Allied soldiers upon entering Nazi concentration camps like Dachau during World War II. Felix L. Sparks, in his remarks at the U.S. Holocaust Museum, describes the harrowing scene soldiers encountered, including rooms filled with emaciated corpses and dead inmates in the yard, highlighting an unprecedented scale and type of death that even battle-hardened soldiers could not easily comprehend.