Final answer:
The sentence that best uses the word "inexhaustible" is: "Her energy seemed inexhaustible as she worked tirelessly."
Step-by-step explanation:
The sentence that best uses the word "inexhaustible" is: "Her energy seemed inexhaustible as she worked tirelessly." In this sentence, "inexhaustible" describes the energy of the person, implying that she had an endless amount of energy and could keep working without getting tired.
In the other sentences, the word "inexhaustible" is not used correctly. For example, in the sentence "The marathon runner felt inexhaustible after he fell to the ground after the race," the word should be "exhausted" instead, as the marathon runner would feel tired and depleted after such a strenuous activity.
Similarly, in the sentence "The gardener planted an inexhaustible variety of flowers," a more appropriate word would be "diverse" or "wide-ranging," rather than "inexhaustible." The word suggests that there is an unlimited supply of flower types, which is not accurate.