An American Indian Mother Expresses Concern About an Irregularly Shaped

An American Indian mother expresses concern about an irregularly shaped, dark area over her neonate's sacrum and buttocks. What is the nurse's most appropriate response to this mother?

A) "This area will continue to grow until the infant is 10 to 15 months old."
B) "This is a birth mark, which usually disappears by age 5 years."
C) "This skin abnormality will require follow-up care."
D) "This is a birth mark and they usually disappear by age 1 or 2 years."