第 16 至 20 題為題組
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. 【題組】19. (A) threaten (B) threatening (C) threatened (D) to threaten