In each of the following independent situations, determine Winston’s filing status for 2021. Winston is not married.

a. Winston lives alone, but he maintains a household in which his parents live. The mother qualifies as Winston’s dependent, but the father does not.

b. Winston lives alone but maintains a household in which his married daughter, Karin, lives. Both Karin and her husband (Winston’s son-in-law) qualify as Winston’s dependents.

c. Winston maintains a household in which he and a family friend, Ward, live. Ward qualifies as Winston’s dependent.

d. Winston maintains a household in which he and his mother-in-law live. Winston’s wife died in 2020.

e. Same as part (d), except that Winston’s wife disappeared (i.e., she did not die) in 2019.