Which of the following is a major hallmark of the period of middle childhood?

Middle childhood (approximately ages 7–11) corresponds to Piaget's concrete operational stage, characterized by the development of logical thought applied to concrete situations. Make-believe play emerges in early childhood (preoperational stage). Rapid motor development and overall physical growth are more pronounced in infancy and adolescence. Abstract scientific reasoning develops in formal operational stage (adolescence). Concrete logical thought is the defining cognitive hallmark of middle childhood.