Scientists have been struggling to find out the reason behind blushing (脸红). Why would humans evolve(进化) a 21____ that puts us at a social disadvantage by 22____ us to reveal that we have cheated or lied? Charles Darwin pointed out that 23____ all people of all races blush，animals do not. When it came to explaining the reason，he was 24____ a loss. That has not stopped others from trying. One 25____ is that blushing started out as a way to show we obey authoritative members of the group. Later，as our social interactions became 26____ complex，it became involved with higher，self-conscious 27____ such as guilt，shame and embarrassment. This would seem to put individuals at a disadvantage，but blushing might actually make a person more 28____ or socially desirable. 29____ that women blush more than men，one university researcher suggests that blushing might have evolved as a way for women to 30____ their honesty to men so as to win their support in raising children. Some zoologists also think blushing could have emerged as a way to foster trust. " If you were to go hunting 31____ a stone-faced partner，you could never 32____ what he wants. “he says. Once blushing became 33____ with embarrassment，anyone who did not blush might have been at a disadvantage because we are 34____ likely to trust someone who appears never to feel 35____ about anything. Scientists have been struggling to find out the reason behind blushing (脸红). Why would humans evolve(进化) a 21____ that puts us at a social disadvantage by 22____ us to reveal that we have cheated or lied? Charles Darwin pointed out that 23____ all people of all races blush，animals do not. When it came to explaining the reason，he was 24____ a loss. That has not stopped others from trying. One 25____ is that blushing started out as a way to show we obey authoritative members of the group. Later，as our social interactions became 26____ complex，it became involved with higher，self-conscious 27____ such as guilt，shame and embarrassment. This would seem to put individuals at a disadvantage，but blushing might actually make a person more 28____ or socially desirable. 29____ that women blush more than men，one university researcher suggests that blushing might have evolved as a way for women to 30____ their honesty to men so as to win their support in raising children. Some zoologists also think blushing could have emerged as a way to foster trust. " If you were to go hunting 31____ a stone-faced partner，you could never 32____ what he wants. “he says. Once blushing became 33____ with embarrassment，anyone who did not blush might have been at a disadvantage because we are 34____ likely to trust someone who appears never to feel 35____ about anything. 

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