Answer:
C. Zeal
Step-by-step explanation:
The best definition of the word "ardor" as used in the second sentence is Zeal.
From the sentence the word is derived, the people are encouraged to pursue learning with ardor because it is not gotten by chance.
The word zeal means great enthusiasm or energy in the pursuit of a cause.
Therefore, the word zeal is the best definition of the word "ardor" in the sentence.