Among Infant-Directed Speech, Adult-Directed Speech, Infant-Directed Singing, and Adult-Directed Singing

Among infant-directed speech, adult-directed speech, infant-directed singing, and adult-directed singing, 6-month-old infants show a preference for

A) any singing over any speech.
B) any speech over any singing.
C) infant-directed singing over infant-directed speech.
D) infant-directed speech over any singing.