Hibemation(冬眠)is a way for some animals to deal with the harshness of winter.They seek out a place where. The will be protected from the weather and stay ___16___ the winter is over.During hibernation aninfals curl up and ___17___ breathe,seeming almost dead.Their hrart rate and blood pressure are greatly ___18___, and their body temperature hovers near the freezing ___19___.When the weather turns warmer,the animals come out of this state and return to ___20___ activities.
Hibermators try to find dark,quiet,safe winter homes where they will not be ___21___.They may make a den more ___22___ by filling it with grass,hair and other materials.In ___23___, many animals that normally hibernate may have to stay active during the winter because of noise and ___24___.
Before winter comes,hibernators spend much of their time eating to ___25___more baby fat.This extra fat keeps them ___26___ during the months when they do not eat.A hibernator's body is sensitive ___27___ weather conditions.At different points during hibernation, these animals will increase their body temperature,move around,eat and then ___28___ to hibermating.An animal that does not do this may freeze to death.Similarly,animals respond to warmer temperatuies ___29___ to come out of hibermation.It may take an hour or more for a hibemation to reach an alert state.
The knowledge on hibemation has been used on patients ___30___certain types of surgery.It may be possible that hibernation could also someday help space travelers by decreasing their need for oxygen and food.
回答第（16）问
A、until
B、before
C、since
D、when
【正确答案】：A
