The quote that shows that the tea ceremony teaches about purity and harmony is the one that states that guests do not speak while tea is being prepared and served so that they can focus on the spiritual aspect of this experience, as shown in the last option of answer.
We can arrive at this answer because:
For this reason, guests at a tea ceremony should not speak while the ceremony is taking place, as they need to concentrate, to bring out the spirit and form the search for purity and harmony.
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