Which of the following potential energy diagram represent an exothermic concerted reaction? 
Definitions:
Conditioning
A behavioral process whereby a response becomes more frequent or predictable in a given environment due to reinforcement.
Epigenetics
The study of heritable changes in gene expression that occur without changes in the DNA sequence itself.
Observational Learning
A learning process in which individuals acquire new behaviors or knowledge by watching and imitating others.
Excoriation Disorder
A mental disorder characterized by the compulsive urge to pick at one's skin to the extent of causing damage.
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