What Is the Definition of System-2 Thinking

What is the definition of System-2 Thinking?

A) reactive thinking that relies heavily on situational cues, salient memories, and heuristic shortcuts to arrive quickly and confidently at judgments
B) reactive thinking that is useful for recalling salient memories and fully supports heuristic thinking at its highest level
C) reflective critical thinking that is useful for judgments in unfamiliar situations, for processing abstract concepts, and for deliberating when there is time for more comprehensive consideration
D) reflective thinking that relies heavily on preconceived notions and is helpful for executing well-trained responses to expected problems