I believe the answer is: double blind procedures
double blind procedures refers to a form of study in which both participants and the researchers do not know which subjects are receiving the treatment. The purpose of double blind procedures is to prevent the bias held by the experimenters along with placebo effects.
The correct answer is C.
The Plessy v. Ferguson was a landmark case from the US Supreme Court, issued in 1896.
It confirmed that segregated facilities were not violating the US constitution as long as the ones for whites and the ones for black citizens were equal in quality. From this decision, the principle "separate but equal" was derived.
It actually gave legitimacy to the Jim Crow laws that many Southern States were enacting, and which promoted segregation and indirect discriminations.
Answer:
D. They created culture enrichment.
One reason it was a health threat is it caused teeth to become ground down which would then lead to infections. The same was true with their eyes and lungs, sand would be blown into their eyes or inhaled into their lungs and then could cause infections.
