Japanese Adults Have Difficulty Distinguishing Between the Sounds R and L

Japanese adults have difficulty distinguishing between the sounds r and l. How skilled are Japanese infants at discriminating between the two sounds?

A) Japanese 6-month-olds exposed to only the Japanese language have as much difficulty discriminating between the sounds r and l as Japanese adults.
B) Japanese 6-month-olds have as much difficulty discriminating between the sounds r and l as Japanese adults, regardless of whether they have been exposed to languages that include the r/l contrast or not.
C) Japanese infants are able to discriminate between the sounds r and l as easily as American infants exposed to languages where the r/l contrast is present.
D) Neither Japanese infants nor American infants are skilled at discriminating between the sounds r and l.