Final answer:
The fourth quartile group is likely to contain the oldest individuals, since bone density decreases with age and the lowest BMD quartile would statistically tend to include older adults.
Step-by-step explanation:
The question asks which Bone Mineral Density (BMD) quartile group likely contains the oldest individuals. Bone density tends to decrease as individuals age, with peak bone mass being reached around 30 years old. As bone density decreases over time, older individuals are likely to have a lower bone mineral density. Thus, without specific data to examine the bone mineral density across different age groups, a generalized assumption can be made that the oldest individuals would be in the fourth quartile group, which would have the lowest bone mineral density. This is due to the natural age-related bone loss as seen in Figure 14.7.3, showing a decrease in bone mass after its peak at about the age of 30 in both males and females.