"This Infamous Decision of the Slaveholding Wing of the Supreme

"This infamous decision of the Slaveholding wing of the Supreme Court maintains that slaves are within the contemplation of the Constitution of the United States,property...The Constitution,as well as the Declaration of Independence,and the sentiments of the founders of the Republic,give us a platform broad enough to support the most comprehensive plans for the freedom and elevation of all the people of this country."
Frederick Douglass,May 1857
-This excerpt would be most useful to historians as a source of information about which of the following?

A) The trial of John Brown
B) The Emancipation Proclamation
C) The Missouri Compromise
D) The Dred Scott decision