Reading Comprehension
试题详情
文章：
| 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. |
题目：
The author of the passage would probably agree with which of the following statements about the SCNs?
选项:
A、The SCNs are found in other organs and tissues of the body besides the hypothalamus.
B、The SCNs play a critical but not exclusive role in regulating circadian rhythms.
C、The SCNs control clock genes in a number of tissues and organs throughout the body.
D、The SCNs are a less significant factor in regulating blood pressure than scientists once believed.
E、The SCNs are less strongly affected by changes in light levels than they are by other external cues.
答案:
B
