In one investigation, researchers followed three adolescent cohorts, each born a year apart, over three years to see if family h
armony changed as the participants experienced dramatic physical and psychological changes. After ruling out ________, the researchers concluded from this ________ design that family closeness declines steadily from sixth to tenth grade.
Billy gets frustrated and starts to cry. He pushes his bike down on the lawn and throws his helmet off. Then he tells his father that he doesn't want to learn how to ride a bike.
