The secondary sex ratio of newborns in the United States is 105 males:100 females. Why doesn't this match the 1:1 predicted primary sex ratio?

A)because males and females have different survival rates between conception and birth
B)because there are often errors in chromosomal segregation at meiosis I
C)because defects in essential sex-determining hormones change the sex of zygotes after fertilization
D)because there is sometimes spontaneous chromosome duplication of the X or Y after development begins