TOP閱讀 Biological clocks插句題 - 英檢

答案為B 但我覺得B選起來有點突兀

我的想法是

A不能選 因為後面有such an

D不能選 drift明顯是連句

C看起來可以 因為後面接著提到external相關 至於為什麼答案要B我就不知道了

懇請解答 謝謝!

Paragraph 3：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. ■Without the external cue, the difference
accumulates and so the internally regulated activities of the biological day
drift continuously, like the tides, in relation to the solar day. ■This
drift has been studied extensively in many animals and in biological
activities ranging from the hatching of fruit fly eggs to wheel running by
squirrels. Light has a predominating influence in setting the clock. Even a
fifteen-minute burst of light in otherwise sustained darkness can reset an
animal's circadian rhythm. Normally, internal rhythms are kept in step by
regular environmental cycles. For instance, if a homing pigeon is to navigate
with its Sun compass, its clock must be properly set by cues provided by the
daylight/darkness cycle.

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.
Where would the sentence best fit?


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