2. 外语
  3. Defined biologically, hair is primarily composed of keratin, a protein, which grows out through the skin from follicles deep wit

Defined biologically, hair is primarily composed of keratin, a protein, which grows out through the skin from follicles deep wit

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问题 Defined biologically, hair is primarily composed of keratin, a protein, which grows out through the skin from follicles deep within the dermis. This definition holds for all mammals. What sets humans apart is not in the hair, but in the follicle. Under the microscope, an individual human’s hair follicles are anatomically indistinguishable, meaning that a hair follicle on your head is visually identical to one on your upper arm. Physiologically, however, the two follicles behave very differently. The first type, found in all mammals, produces terminal hair, the longer, darker, thicker hair generally found on the scalp, eyebrows, and eyelashes. The second type, particular to humans, produces the fine, unpigmented vellus hair found on most places of the human body, including the face and back. Vellus hair is usually very short and the follicles are not connected to sebaceous glands.
Which of the following, if true, most weakens the author’s argument that human hair is distinct from the hair of other mammals?
选项 A、Scientific research shows that both vellus hair follicles and terminal hair follicles develop from a common follicle stem cell.
B、Keratin has been found to exist in cells other than hair cells.
C、Other animals, including insects and spiders, have been categorized as having hair-like filaments.
D、Vellus hair follicles have been identified on chimpanzees.
E、Hair follicle stem cells are also responsible for new skin growth after injury.
答案D
解析 The best answer is D. The author argues that humans are unique in having vellus hair follicles in addition to terminal hair follicles. If another mammal were found also to have vellus hair follicles, humans would no longer be unique, and the author’s argument would collapse. The other answer choices are outside the scope of the passage or are irrelevant to the author’s argument.
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