Final answer:
The 30-year-old with weakness, unintentional weight loss, and exhaustion closely meet the definition of “failure to thrive”, as these symptoms reflect substantial complications related to undernutrition and significant health decline.
Step-by-step explanation:
The concept of “failure to thrive” often applies to a clinical condition primarily seen in pediatric and elderly populations, wherein individuals do not gain or maintain adequate weight, sometimes accompanied by a lack of necessary physiological development. Symptoms common to this condition can include weakness, unintentional weight loss, exhaustion, and an inability to endure even minor stress without significant health setbacks. In the context of the clients described, it can be inferred that the client who best meets the definition of “failure to thrive” is a 30-year-old with weakness, unintentional weight loss, and exhaustion, as these symptoms are closely related to undernutrition and the body's catabolic response to starvation.