The passage talks about Dr. Kisilevsky's research which proves that voice recognition of a fetus begins before its birth. The passage also mentions the previous research (not that of Dr.Kisilevsky) on infant development which demonstrates that newborns prefer to listen to their own mother's voice than to that of a female stranger. Options B and C are not mentioned in the passage. Between A and D, D is the correct answer as option A says that the previous research was conducted by Dr.Kisilevsky, which is incorrect.