In which of the following cases may the taxpayer claim head of household filing status?
a. The taxpayer is single and maintains a household that is the principal place of abode of her infant son.
b. The taxpayer is single, maintains a household for herself, and maintains a separate household that is the principal place of abode of her dependent widowed mother.
c. The taxpayer was married from January to October and lived with his spouse from January to May. From June 1 to December 31, the taxpayer maintained a household that was the principal place of abode of his married son and daughter-in-law, whom the taxpayer can claim as dependents.
d. Same as (c) except the taxpayer lived with his ex-spouse until August and maintained the household from September 1 to the end of the year.