Which of the following taxpayers qualifies to claim the child tax credit? 1) A taxpayer who files as head of household and claims his 18-year-old daughter as a dependent. 2) A divorced taxpayer who claims his 15-year-old son as a dependent. The son lives most of the year with the ex-wife. The taxpayer was given the dependency exemption when the ex-wife signed away her right to claim the son as her dependent. 3) A 25-year-old unmarried taxpayer who claims her 10-year-old sister as a dependent 4) both b. and C. 5) both a. and b. a