Final answer:
Cognitive Psychology (D) is the field of psychology that studies the mental processes involved in acquiring, storing, and using knowledge, focusing on how and why we think the way we do.
Step-by-step explanation:
The branch of psychology that focuses on the mental processes involved in acquiring, storing, and using knowledge is Cognitive Psychology (D). Cognitive psychology is dedicated to examining how people think, and it attempts to explain how and why we think the way we do. It encompasses a variety of mental aspects, including human thinking, human behavior, and the cognitive revolution which redirected attention back to mental processes rather than just observable behavior.
As part of the cognitive revolution, the field began to analyze cognitions extensively and how these mental processes relate to experiences and actions. The interdisciplinary nature of cognitive psychology is often recognized under the term cognitive science, showing its broad scope and collaboration among various disciplines. Cognitive psychologists study interactions among thinking, emotion, creativity, language, and problem-solving, alongside other cognitive processes.