Question 21 is based on the passage you have just heard.

听力原文：

    Dogs, man’s best friends, have a clear strategy for dealing with angry owners—they look away.

    （19） New research shows that dogs limit their eye contact with angry humans. The scientists suggest this may be an attempt to calm humans down. This behavior may have evolved as dogs gradually learned they could benefit from avoiding conflicts with humans.

    To conduct the tests, the University of Helsinki researchers trained 31 dogs to rest in front of a video screen. Facial photos of dogs and humans were displayed on the screen for 1.5 seconds. They showed threatening, pleasant and neutral expressions. Nearby cameras tracked the dogs’ eye movements.

    Dogs in the study looked most at the eyes of humans and other dogs to sense their emotions. （20）When dogs looked at expressions of angry dogs, their eyes rested more on the mouth, perhaps to interpret the threatening expressions. And when looking at angry humans, they tended to turn away their gaze.

    Dogs may have learned to detect threat signs from humans and respond by trying to make peace, according to researcher Sanni Somppi. Avoiding conflicts may have helped dogs develop better bonds with humans.

    The researchers also note that dogs scan faces as a whole to sense how people are feeling, instead of focusing on a given feature. （21）They suggest this indicates that dogs aren’t sensing emotions from a single feature, but piecing together information from all facial features just as humans do.

21. How does a dog sense people’s feelings?

解析：C。本题目为细节题。问题为：狗如何感受人的情绪？出题位置为：尾段尾句。根据原文“They suggest this indicates that dogs aren’t sensing emotions from a single feature, but piecing together information from all facial features just as humans do.”，可见狗不会通过单独的特征来感受情绪，而是会像人类一样，综合面部所有特征。选项C）By taking in their facial expressions as a whole（通过把面部表情整合为一个整体），与原文信息相一致，其中whole和原文中的all 为同义替换。