Vivid imagery
The answer choices about facts and statistics and quotations should immediately be eliminated. There are no statistics or quotations anywhere in the excerpt. The speaker does not use neutral language when he says words like quaint, incendiary, and uninflected. All of these carry an opinion. Vivid imagery is correct because of the way he talks about the different groups and their locations.
If it is picking out a sentence in the paragraph, I would say "Researchers have been able to use this inherent intelligence to teach Koko sign language.
