Why does piaget use the term "concrete" to describe the quality of thinking that is characteristic of middle childhood?

The correct option is this: THE TERM HIGHLIGHTS THE FOCUS ON REAL OBJECTS RATHER THAN HYPOTHETICAL SITUATIONS AND RELATIONSHIP.
There are four major periods of growth and development, which ranges from birth to age 18. These periods are infancy, early childhood, middle childhood and adolescence. The middle childhood occurs between the ages of 9 and 11 years old. During this period, the level of thinking of children at this age is no more abstract, it is more real and their cognitive abilities develop rapidly.

Yes all of them are right

Clean air provides nitrogen