But 17 is this helpful to us as a response to fear or cold?
答案：(A) how
語意疑問句「但這對我們作為對恐懼或寒冷的反應有『何』幫助？」，how（如何）符合這種質疑用途的疑問句；where（哪裡）、what（不能這樣接is this helpful這種結構）、whether（是否，不能這樣開頭構成直接疑問句）都不合。
本題大考中心未公布逐題答對率，以下不談數據，只談觀念。
四個選項都是 wh- 詞，而 what 是最常用的一個，看到問句就想用它。這一格要先數空格後面那個句子缺不缺成分。
先數成分：___ is this helpful to us as a response to fear or cold?主詞是 this、動詞是 is、補語是 helpful，成分一個都不缺。既然不缺，what 就先出局——它是名詞性的疑問詞，進到句子裡一定要占一個位置（當主詞、受詞或補語），這裡沒有位置給它。（同判準：93 年第 18 題、91 年第 25 題、90 年第 20 題、87 年第 26 題、84 年第 30 題。）剩下 how、where、whether，用語意分：前一句才講完雞皮疙瘩是怎麼形成的，這一句用 But 一轉，要問的是「這東西對我們到底有什麼用」——問的是方式與用處，填 how。How is this helpful to us? 就是「這對我們有何幫助」。
what：成分已滿，塞不進去。where（哪裡）：問地點，與「有沒有用」無關。whether（是否）：它帶出的是名詞子句，不能直接放在句首構成一個帶問號的直接問句。
How is this helpful?（這有什麼幫助）、be helpful to sb（對某人有幫助）、a response to（對……的反應）、fight-or-flight（戰或逃）、contract involuntarily（不由自主地收縮）、back in the days when …（在……的那個年代）。
Goose bumps are one of those fight-or-flight reactions of the sympathetic nervous system. When you experience cold or fear, a nerve reaction is sent to the muscles, which then contract involuntarily. This muscle contraction causes your body hair to stand erect. The skin with standing body hair 16 a goose's skin after its feathers have been plucked—hence the name goose bumps. But 17 is this helpful to us as a response to fear or cold?
Back in the days when our ancestors may have had a lot more body hair, this might have helped to keep them warm or scare an oncoming predator. These days, however, goose bumps are 18 to human beings.
Goose bumps, or the reflex that causes them, also occur in many other mammals. Many mammals fluff up their fur when 19 , to look bigger and thus more dangerous. For example, when a porcupine encounters a predator, its long sharp pointed hairs will stand up as a means of 20 . In animals with a thick hair coat, the rising of hair traps more air between the hairs, providing another layer of insulation to keep them warm.