Taking one's own children as the research object, the educator who wrote three masterpieces on children's psychological development is ().

A. Piaget

B. Freppel

C. Dewey

D. Gardner

Check the answer analysis [answer] a

[Analysis] Piaget also put the research object on his three children, and recorded their every move, words and deeds in detail from birth. After years of observation and research, he wrote three important books about children's psychological development.