Answer:
Based on the context, the word "wan" most likely means C. strained.
Step-by-step explanation:
Both adjectives, wan and strained, may refer to someone or something who looks tired, exhausted. Even if we didn't know that, we could reach that conclusion through context clues. In the excerpt we are studying here, the narrator tells us that Mr. Smith has previously argued with very strong language. However, he is no longer arguing. It sounds as if he's gotten tired of it, as if he has no strength to do it anymore. He only offers a wan, pale, strained, tired smile in return to what is being said to him.