How did trade affect early human society

In a democracy, this is held by the citizens who elect leaders to political office

Which of the following studies is linked most directly to the establishment of the national research act in 1974 and ultimately to the belmont report and federal regulations for human subject protection? a. the public health service tuskegee study of untreated syphilis in the negro male.b. stanford prison experiment (zimbardo).c. tearoom trade study (humphreys).d. the harvard t3 study.

What period of history refers to the time when people did not have written records