TPO13 Biological Clocks - 英檢

Like almost all daily cycles of animals deprived of environmental cues, those
measured for the horseshoe crabs in these conditions were not exactly 24
hours. Such a rhythm whose period is approximately—but not exactly—a day is
called circadian. For different individual horseshoe crabs, the circadian
period ranged from 22.2 to 25.5 hours.

10. In paragraph 2, why does the author mention that the period for different
horseshoe crabs ranges from 22.2 to 25.5 hours?
A) To illustrate that an animal's internal clock seldom has a 24-hour cycle
B) To argue that different horseshoe crabs will shift from daytime to
nighttime vision at different times
C) To illustrate the approximate range of the circadian rhythm of all animals
D) To support the idea that external cues are the only factors affecting an
animal's periodic behavior
答案是A!我選C
想請教AC兩個要怎麼區分呢?是根據上面哪一個句子?
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Animals need natural periodic signals like sunrise to maintain a cycle whose
period is precisely 24 hours. ■Such an external cue not only coordinates an
animal's daily rhythms with particular features of the local solar day but
also—because 【it 】normally does so day after day-seems to keep the
internal clock's period close to that of Earth's rotation. ■Yet despite this
synchronization of the period of the internal cycle, the animal's timer
itself continues to have its own genetically built-in period close to, but
different from, 24 hours.

13. Look at the four squares [■] that indicate where the following sentence
could be added to the passage.

Because the internal signals that regulate waking and going to sleep tend to
align themselves with these external cues, the external clock appears to
dominate the internal clock.

我一直在上面這兩格猶豫!答案是給第二格!!可是我最後還是選第一格!
每次都選錯的答案XD可以請大家幫忙一下有什麼根據嗎?
謝謝!!
非常謝謝大家!!!

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