Final answer:
The stage in Piaget's theory that starts in adolescence and continues into adulthood is the formal operational stage (d). This stage involves the ability to think abstractly and hypothesize, allowing for advanced problem-solving and discussion of complex topics.
Step-by-step explanation:
The stage in Piaget's theory of cognitive development that begins in adolescence and continues through adulthood is d) Formal operational stage. This stage, typically starting around age 11, marks a significant shift where individuals move beyond concrete thinking and begin to comprehend abstract concepts and hypothetical situations. Thinkers in the formal operational stage can use abstract thinking to problem-solve, consider alternative solutions, and methodically test these ideas.
During the concrete operational stage, which occurs from about 7 to 11 years of age, children can think logically about tangible, concrete things. However, it is only in the formal operational stage that they can deal with abstract reasoning. This developmental milestone allows them to engage in sophisticated thought processes such as considering multiple points of view, imagining different outcomes to situations, and discussing various ideas and beliefs.
Although Piaget's theory of cognitive development, which includes the sensorimotor, preoperational, concrete operational, and formal operational stages, has been fundamental to our understanding of developmental psychology, it has also been subject to revision.
Subsequent research suggests that cognitive development could be more continuous and that children might achieve certain cognitive milestones earlier than Piaget posited. Some developmental psychologists have even proposed a fifth, post-formal stage, where logic is integrated with emotion and decisions are more context-based.