A historian wants to use the historical thinking skill of synthesis to better understand the influence of Lincoln's Emancipation Proclamation on Harry S. Truman. Which of the following actions would he need to take before he could use this skill?
A. Research Lincoln's orders to the military concerning segregation
B. Research the lasting impact of Truman's use of the executive order
C. Determine the historical period that produced the Emancipation Proclamation
D. Identify Truman's motives for issuing Executive Order 9981
