CAFS Preliminary Practice Exam - Practice Test & Study Guide

The correct answer is 15 years because, according to the Australian Bureau of Statistics (ABS) definition, at least one member of a family should be 15 years or older to qualify as part of the household unit. This age threshold reflects a point at which individuals are expected to engage more with societal structures, such as education and employment, thus having a more defined role within the family unit.

In demographic studies, this age is significant as it aligns with the age at which individuals may be considered capable of contributing to family dynamics and responsibilities. The other age options do not correspond to the ABS definition for family classifications, as they either are not indicative of a young person's ability to participate in the family unit or do not align with the commonly acknowledged thresholds used in demographic statistics.