What reason does Elizabeth give for choosing to believe Wickham?

One reason Elizabeth chooses to believe Wickham was that he "appeared" to be telling the truth. This answer can be found in Chapter Seventeen. If your question pertains to another chapter, please advise.

"I can much more easily believe Mr. Bingley's being imposed on, than that Mr. Wickham should invent such a history of himself as he gave me last night; names, facts, everything mentioned without ceremony. If it be not so, let Mr. Darcy contradict it. Besides, there was truth in his looks."

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