Piaget believed that in each stage, children a. learn most effectively through lecture. b. build knowledge. c. need constant external motivation. d. need to use workbook pages to learn math.

C. need constant external motivations they have  sensorimotor, preoperational, concrete, and formal stages of development.

Explanation:

Piaget first developed himself as a psychologist in the early 1920's and investigated the hidden side of the children's mind, and proposed that children, moved to form a period of egocentrism to the sociocentrism.   Thus Piaget theorized that the children did this due to the social interactions and the challenge that is linked to the young children's ideas by the ideas of those children who were more advanced. Thus more attention was on the cognitive stage.