Which of the following terms is related to the decline or weakening due to neglect?

The term that best relates to the decline or weakening due to neglect is "atrophies." This word specifically refers to the process where something decreases in size, effectiveness, or vigor, often as a result of disuse or neglect. In various contexts, atrophy can refer to muscle wasting due to lack of exercise or, more broadly, to a deterioration in function or vitality, indicating a significant decline caused by inadequate attention or care.

In contrast, "prolific" describes something that produces abundantly or is very fruitful, which has no connection to decline or neglect. "Ebullient" refers to being exuberant or enthusiastic, conveying energy and liveliness, which is opposite to the idea of decline. "Lethargic" indicates a state of sluggishness or inactivity, which might suggest a lack of energy but does not inherently imply a decline due to neglect in the same way that atrophies does.