Professor ober carefully observes and records the behaviors of children in their classrooms in order to track the development of their social and intellectual skills. professor ober is most clearly engaged in

naturalistic observation

Explanation:

Naturalistic observation refers to the type of research that conducted by observing the subjects' uncontrolled behavior when they are in their natural environment.

If the professor want to observe how children develop their social and intellectual skills, the school classroom is considered as the perfect natural environment because in this place children will show how they gather around the people that they like and form a close friendship with them. It also provide the data on how children would response to the teaching method and materials that the teacher gave them.

1) d

2)c

3)b

4) a

5)c

6) c

industry had made the u.s. the richest nation in the world at this time. the second industrial revolution caused growth in industry and transportation, which allowed increased trade between nations.