Final answer:
The sentence from Choe's answer that refers to the spread of bad luck in the same way that learning and civilization had spread supports the idea that a bad mood is contagious. It illustrates how a mood or emotional state can disseminate through a society, adding credence to the notion that moods can be transferred from one individual to another.
Step-by-step explanation:
To determine which sentence from the passage best supports the answer to whether a bad mood is contagious, we'll look at the supplied references. The passage that mentions 'Choe's answer to his last question was that the bad luck of Tang had spread, as its learning and civilization had spread earlier, infecting Silla.' is the most pertinent. This indicates that like the spreading of learning and civilization, bad luck, and as an extension, a bad mood, can spread and influence others. The idea that a mood, emotion, or state of being, such as bad luck, can disseminate through society, supports the notion of the contagion of moods.
This concept is further illustrated by this publication: Vella, E. J., Kamarck, T. W., Flory, J. D., & Manuck, S. (2012). Hostile mood and social strain during daily life: A test of the transactional model. Annals of Behavioral Medicine, 44, 341-352. It suggests that mood, specifically a hostile one, can be part of social interactions and influenced by daily events, implying the transmissibility of moods between individuals.