In April of Year 1, Martin Left His Wife, Marianne

In April of Year 1, Martin left his wife, Marianne. The couple has two children under the age of 15. While the couple was apart, they were not legally divorced. Marianne remained in the home and paid all the costs of maintaining the home for the remainder of the year. Assuming the couple does not file jointly, which of the following statements regarding filing status is true?

A) No matter the post-separation residence(s) of the children, both spouses must file as married filing separately.
B) No matter the post-separation residence(s) of the children, Martin must file as married filing separately but Marianne may qualify to file as head of household.
C) No matter the post-separation residence(s) of the children, Marianne must file as married filing separately but Martin may qualify to file as head of household.
D) Depending on the post-separation residence(s) of the children, both spouses may qualify to file as head of household.