Which of the Following Events Results in X-Inactivation in Female

Which of the following events results in X-inactivation in female mammals?

A) activation of the XIST gene on the X chromosome that will become the Barr body
B) activation of the BARR gene on one X chromosome, which then becomes inactive
C) inactivation of the XIST gene on the X chromosome derived from the male parent
D) attachment of methyl (-CH3) groups to the X chromosome that will remain active