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(单选题)Why does coffee in white cups taste the least sweet? (单选题)What color of the cup can best reduce coffer’s bitterness wi (单选题)What did Robin learn from the story? (单选题)What did Robin's mother do? (单选题)Why did two boys come to the restaurant? (单选题)Which of the following caused some people to leave their tab (单选题)According to Dr. Singer, ______. (单选题)From the article, we can know that ______. (单选题)The author used the example of “dice” to show that ______. (单选题)In how many ways do toys change according to the first parag