Answer:
physical
Explanation:
Physical development: The term physical development is defined as a phenomenon that generally starts in an individual's infancy period and lasts through the late adolescent period that concentrates on fine and gross motor skills and puberty.
It develops an individual's control over his or her body, physical coordination and particularly muscles. It plays an important role in an individual's life and slowly degrades as the individual's age increases.
In the question above, the researcher most likely studying physical development.