Whose Social Security benefit is included in the calculation of the maximum family benefit for those eligible for benefits based on a retired worker's fully insured status?
I. The retired worker's benefit.
II. A caregiver spouse's benefit for caring for a qualified disabled child.
III. A dependent child's benefit.
IV. The retired worker's former spouse.
a. III and IV.
b. I, III, and IV.
c. I, II, and III.
d. I and II.