What is the difference between the U-3 Rate and the U-6 Rate?

Read a report of the paris medical faculty from 1348 about the plague. we can say that the main cause of this pestilence was and is the configuration of the heavens. in 1345, at 1: 00 in the afternoon of march 20th, there was a major conjunction of three planets in the constellation of aquarius. this conjunction, along with others like it and the eclipse caused a deadly corruption of the air around us. what is the most likely reason this document would be important to a historian’s study of the black death? a) it shows the importance of astronomy in medicine today. b) it shows how medicine once differed in paris and london. c) it shows how the plague’s cause was interpreted in the past. d) it shows the desperation to find a cause of the black death.