Which of the Following Features of the Monkey Experiment Conducted

Which of the following features of the monkey experiment conducted by Margaret and Harry Barlow is the most important in demonstrating the importance of the emotional relation between a mother and her child?

A) that even with less milk the monkeys responded better to the cloth covered fake mother
B) that monkeys responded well to fake mothers
C) that they used a control group and an experimental group
D) that they used a species of animal that was close in many ways to humans