In a Research Study on Newborn Preferences, How Did the Researchers

In a research study on newborn preferences, how did the researchers determine that a newborn preferred their mom's scent over other women's scents?

A) The newborn nuzzled up to a gauze pad with the mom's scent on it longer than the other women's gauze pads.
B) The newborn nuzzled up to the mom's shoulders longer than the other women's shoulders.
C) The newborn stared at the mom's face longer than they stared at the other women's faces.
D) The newborn fell asleep in the mom's arms and did not fall asleep in the other women's arms.