d.) a sudden flash of understanding.
Explanation:
Insight is an English term used in psychology to define the moment we become aware or realize something; be it about our problems (or a solution to one), our mood, our emotions, our thoughts, etc. That is, an insight is a sudden flash of understanding.
On many occasions, we experience a series of moods unknowingly, noticing only feelings of discomfort or well-being, but not quite understanding how we feel. It is the moment we become able to understand these emotions or what made us feel that way that we can keep moving forward. Thus, through insight, the person grasps or understands a revealed “truth”. It can happen suddenly, after deep work, or through adapted techniques.