Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. Stability, a feature of the biological clock's period, depends on changeable factors such as temperature. B. A major feature of the biological clock is that its period does not change despite significant changes in the environment. C. A factor such as temperature is an important feature in the establishment of the biological clock's period. D. Biological activity is not strongly affected by changes in temperature.