Which of the following taxpayers must file a 2019 return? a. Amy, age 19 and single, has $8,050 of wages, $800 of interest, and $350 of self-employment income. b. Betty, age 67 and single, has a taxable pension of $9,100 and Social Security benefits of $6,200 (the Social Security benefits are wholly-tax exempt in this situation). c. Chris, age 15 and single, his a dependent of his parents. Chris has earned income of $1,900 and interest of $400. d. Dawn, age 15 and single, is a dependent of her parents. She has earned income of $400 and interest of $1,600. e. Doug, age 25, and his wife are separated. He earned $5,000 while attending school during the year.