GWD上一篇，关于取非题我不太明白~请大家帮忙~

郭happy

GWD-1-第三篇阅读

      Recently biologists have been interested in atide-associated periodic behavior displayed by the diatom Hantzschia virgata, a microscopic golden-brown alga that inhabitsthat portion of a shoreline washed by tides (the intertidal zone). Diatoms ofthis species, sometimes called “commuter” diatoms, remain burrowed in the sandduring high tide, and emerge on the sand surface during the daytime low tide.Just before the sand is inundated by the rising tide, the diatoms burrowagain.  Some scientists hypothesize thatcommuter diatoms know that it is low tide because they sense an environmentalchange, such as an alteration in temperature or a change in pressure caused bytidal movement.  However, when diatomsare observed under constant conditions in a laboratory, they still display periodicbehavior, continuing to burrow on schedule for several weeks. This indicatesthat commuter diatoms, rather than relying on environmental cues to keep time,possess an internal pacemaker or biological clock that enables them toanticipate periodic changes in the environment. A commuter diatom has anunusually accurate biological clock, a consequence of the unrelentingenvironmental pressures to which it is subjected; any diatoms that do notburrow before the tide arrives are washed away.

      This is not to suggest that the period ofthis biological clock is immutably fixed. Biologists have concluded that even though a diatom does not rely on theenvironment to keep time, environmental factors—including changes in the tide’shydrostatic pressure, salinity, mechanical agitation, and temperature—can alterthe period of its biological clock according to changes in the tidalcycle.  In short, the relation between anorganism’s biological clock and its environment is similar to that between awristwatch and its owner:  the ownercannot make the watch run faster or slower, but can reset the hands. However, this relation is complicated inintertidal dwellers such as commuter diatoms by the fact that these organismsare exposed to the solar-day cycle as well as to the tidal cycle, and sometimesdisplay both solar-day and tidal periods in a single behavior. Commuterdiatoms, for example, emerge only during those low tides that occur during theday.

GWD18-Q23

题目：对应原文划线句的话

Which of the following can be inferred from the passage about the effect ofthe solar-day cycle on the tide-associatedperiodic behavior displayed by commuter diatoms?

• The solar-day cycle makes this behavior less advantageous to the commuter diatoms at certain times of     the year. 无
• The solar-day cycle makes this behavior somewhat more erratic. 无
• The solar-day cycle makes this behavior less important to the survival of the commuter diatoms. 无
• Because of the solar-day cycle, this behavior is forced to proceed at a more rapid pace at certain times     during the 24-hour day. 无
• Because of the solar-day cycle, this behavior is not expressed at certain times     during the 24-hour day. 取非
  

取非是什么意思啊？E答案用到取非的方法了吗？看不太明白

郭happy

自己顶一下~~~有没有人啊~