The correct answer is: A. Fatigue : Exercise
In the original pair, “darkness” is the absence of light, and “lamp” is a source of light. In the answer pair, “fatigue” is the absence of energy, and “exercise” is a way to get energy. Both pairs have a similar relationship, in that one word describes a state or condition, and the other word describes something that can be used to change or improve that state or condition.
The other options are incorrect because they do not have the same relationship as the original pair. In option B, “thirst” is a desire for water, but water is not something that can be used to change or improve thirst. In option C, “medicine” is a treatment for illness, but illness is not something that can be used to change or improve medicine. In option D, “study” is a way to learn, but a classroom is not something that can be used to change or improve study.