51. What does the passage say about infants learning the category “dog” if they are exposed to Chihuahuas only?
- A. They will encounter some degree of difficulty.
- B. They will try to categorise other objects first.
- C. They will prefer Chihuahuas to other dog species.
- D. They will imagine Chihuahuas in various conditions.
答案：A
答案句：For instance, infants will struggle to learn the category “dog” if they are only exposed to Chihuahuas, instead of many different kinds of dogs.
参考译文：例如，如果婴儿只接触吉娃娃，而不是许多不同种类的狗，他们将难以学习“狗”这一类别。
定位线索：题干“infants learning the category 'dog' if they are exposed to Chihuahuas only”对应答案句“infants will struggle to learn the category 'dog' if they are only exposed to Chihuahuas”；文中“struggle”对应选项A“encounter some degree of difficulty”。
解析：题干问婴儿只接触吉娃娃学习“狗”类别的情况，答案句直接说明“infants will struggle”，即他们会遇到困难，与选项A“They will encounter some degree of difficulty”同义。选项B“先分类其他物体”无中生有；选项C“偏好吉娃娃”和选项D“想象各种条件”均未提及。