The primary purpose of the passage is to_出国考试答疑器_GMAT

Line	Scientists long believed that two nerve clusters in
	the human hypothalamus, called suprachiasmatic
	nuclei (SCNs), were what controlled our circadian
	rhythms. Those rhythms are the biological cycles
(5)	that recur approximately every 24 hours in
	synchronization with the cycle of sunlight and
	darkness caused by Earth’s rotation. Studies have
	demonstrated that in some animals, the SCNs
	control daily fluctuations in blood pressure, body
(10)	temperature, activity level, and alertness, as well as
	the nighttime release of the sleep-promoting agent
	melatonin. Furthermore, cells in the human retina
	dedicated to transmitting information about light
	levels to the SCNs have recently been discovered.
(15)	Four critical genes governing circadian cycles
	have been found to be active in every tissue,
	however, not just the SCNs, of flies, mice, and
	humans. In addition, when laboratory rats that
	usually ate at will were fed only once a day, peak
(20)	activity of a clock gene in their livers shifted by
	12 hours, whereas the same clock gene in the
	SCNs remained synchronized with light cycles. While
	scientists do not dispute the role of the SCNs in
	controlling core functions such as the regulation of
(25)	body temperature and blood pressure, scientists
	now believe that circadian clocks in other organs
	and tissues may respond to external cues other than
	light—including temperature changes—that recur
	regularly every 24 hours.

The primary purpose of the passage is to

A、challenge recent findings that appear to contradict earlier findings

B、present two sides of an ongoing scientific debate

C、report answers to several questions that have long puzzled researchers

D、discuss evidence that has caused a long-standing belief to be revised

E、attempt to explain a commonly misunderstood biological phenomenon

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老师我感觉这篇文章很简单，可是还是错了两个，我不知道是不是自己做题方法不对，还是粗心，Tina老师您可以讲一下这道题的做题思路吗

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