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  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.
It can be inferred from the passage that
选项 A、mammals do not have sebaceous glands.
B、animals such as monkeys cannot grow terminal hair.
C、the hair of a horse is composed mainly of keratin.
D、scientists cannot distinguish human hair from the hair of other mammals.
E、terminal hair grows much faster than vellus hair.
答案C
解析 The best answer is C. According to the passage, "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." Therefore, a horse has hair that is mainly composed of keratin. The other answer choices are not supported by the passage.
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