Imagine a graph. The x-axis is labeled "time" and is measured in seconds, and the y-axis is labeled "potential energy" and is measured in kilojoules. The slope starts at 0 seconds with a plateau at 25 kJ. This plateau is labeled "reactants". The slope the rises to a peak labeled "activation energy" at 78 kJ. Finally the slope drops to a plateau at 14 Kj and is labeled "products". What does the graph described represent?
A. a phase change graph
B. an endothermic reaction
C. and exothermic reaction
D. a rate of reaction graph