This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
Total space analysis by Merrifield requires: 
Select and explain. 
A. Study cast and radiograph, B. Study cast and reference table, C. Study cast and cephalogram, D. All of the above
C: Study cast and cephalogram
Answer: C: Study cast and cephalogram 
Explanation: Total space analysis by Merrifield;

Requires study casts and cephalograms.
Divides the lower arch into anterior, middle and posterior areas.
The discrepancy for each area is calculated and the resultant value is added to yield the total discrepancy of the arch.

Total space analysis as described by Merrifield is divided into three parts anterior, midarch and posterior.
This is done for simplicity in identifying the area of space deficit or surplus, as well as accuracy in differential diagnosis.
Ref: Graber 6th edition