Question $1(1$ point$)$

According to Kate Brown, why is it hard to prove that Ernest Johnson died from exposure to radiation while working at the Hanford plant?

He was also present at the detonation of the first atomic bombs and may have been exposed to radiation then

An autopsy was never performed on his body before it was burned Hanford officials kept poor records on accidents and sought to keep information from the public

He died at a time when the factory had ceased to produce any measurable amount of radiation.