Which family member exposed to tuberculosis is at the highest risk for contracting the disease?

The selected answer is correct because older adults, particularly those over the age of 65, are at a significantly higher risk for contracting tuberculosis (TB). This vulnerability is due to a combination of factors, including a generally weaker immune system, decreased physiological reserves, and a higher likelihood of having underlying health conditions that can exacerbate the disease.

In this case, the 76-year-old grandmother falls into this high-risk demographic. Older adults may also have had greater exposure to TB throughout their lives, as they have lived longer in environments where TB may be more prevalent.

In contrast, while younger individuals can contract the disease, adolescents and children are generally at lower risk than older adults when considering common epidemiological statistics. The 45-year-old mother and the 17-year-old daughter, while also at risk, do not have the same elevated risk factors associated with age as the grandmother. The 8-year-old son is even less likely to be at high risk when compared to an elderly adult. Therefore, the grandmother represents the group most susceptible to contracting TB in this scenario.