Caroline holds her newborn baby in her arms and watches as the baby gazes at her. The baby seems to be staring at a spot on Caroline's forehead. She wonders what is so interesting about her forehead. What explanation can you give for this?

a. Babies tend to gaze at the eyes and mouth of a face.
b. Babies recognize an inner eye just above the eyebrows.
c. Babies tend to focus attention on borders and contours; the hairline is a type of border.
d. Babies are looking for a sign of contentment on the mother's face which is expressed on the forehead.

c