In which of the following situations is the taxpayer not required to file a 2021 income tax return?

a.When an individual has a current year income tax refund and would like to obtain it.

b.When the taxpayer is a 35-year-old head of household with wages of $18,900.

c.When the taxpayer is a single 67-year-old with wages of $9,800.

d.When the taxpayers are a married couple with both spouses under 65 years old with wages of $26,000.

e.When the taxpayer is a 69-year-old widow (spouse died 3 years ago) with wages of $16,500 and no dependents.