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
What technique of polymerization is shown in the graph? 
Select and explain. 
A. Pulse polymerization, B. Delayed polymerization, C. High intensity polymerization, D. Ramp cure polymerization
A: Pulse polymerization
Answer: A: Pulse polymerization 
Explanation: A concept that may be used to reduce shrinkage stress is the use of “soft-start” polymerization. This approach utilizes a number of procedures to prolong the gel phase of the setting reaction of the composite resin material. The theory is that the longer the setting composite can maintain a gel or flowable condition, the better it can distribute the stresses resulting from shrinking. Procedures to do this include the use of ramped lights, pulse curing, or simply holding the curing light some distance from the material for the initial exposure.