Which of the following taxpayers qualifies for the maximum individual retirement account deduction for 2015?

a A single taxpayer, who is covered by a qualified retirement plan, with adjusted gross income of $80,000

b Married taxpayers, only one of whom is covered by a qualified retirement plan, with total adjusted gross income of $190,000

c A single taxpayer, who is not covered by a qualified retirement plan, with no earned income but with unearned income of $12,000

d Married taxpayers, neither of whom is covered by a qualified retirement plan, with total adjusted gross income, all earned, of $85,000