Concept:Hermann Ebbinghaus pioneered the study of memory and created the retention curve to show how information is forgotten over time.Explanation:Ebbinghaus conducted experiments on himself to understand memory. He plotted the rate at which learned material is retained or forgotten. This graph is called a retention curve, also known as the forgetting curve. It illustrates how memory declines with time after initial learning. No other psychologist listed is associated with designing these curves.Answer:A. Ebbinghaus