In which stage of the lifespan do infancy and adulthood occur?

The correct choice highlights that infancy and adulthood are both recognized as specific stages within the broader framework of the lifespan. This framework encompasses all developmental phases from birth through old age, including infancy, childhood, adolescence, adulthood, and later life.

Infancy is classified as the initial stage, where significant physical and cognitive developments occur, while adulthood represents a later stage characterized by maturity, independence, and often a higher responsibility in personal and professional aspects of life. Recognizing that both stages are part of the diverse and continuous progression of human development underscores the comprehensive nature of the lifespan perspective in understanding human growth and changes over time.

In contrast, the other choices do not represent the entire spectrum of human development. Adolescence and middle age are specific phases that occur between infancy and adulthood, while early childhood pertains to a particular segment of the younger years, leaving significant developmental periods unacknowledged. This comprehensive understanding reinforces the importance of viewing human development as a series of interconnected stages.