ＧＷＤ２３－３３如何定位？谢谢！

debralee

请教大家：以下题目答案是Ｅ，如何定位呀？谢谢！

 

Q33 to Q36:

      Recently biologists have been

         interested in a tide-associated

         periodic behavior displayed by

Line  the diatom Hantzschia virgata, a

  (5)  microscopic golden-brown alga that

inhabits that portion of a shoreline

washed by tides (the intertidal zone).

Diatoms of this species, sometimes

called “commuter” diatoms, remain

 (10)  burrowed in the sand during high

tide, and emerge on the sand sur-

face during the daytime low tide.

Just before the sand is inundated by

the rising tide, the diatoms burrow

 (15)  again.  Some scientists hypothesize

that commuter diatoms know that it

is low tide because they sense an

environmental change, such as an

alteration in temperature or a change

 (20)  in pressure caused by tidal move-

         ment.  However, when diatoms are

         observed under constant conditions

in a laboratory, they still display

periodic behavior, continuing to bur-

 (25)  row on schedule for several weeks.

This indicates that commuter diatoms,

rather than relying on environmental

cues to keep time, possess an inter-

nal pacemaker or biological clock

 (30)  that enables them to anticipate peri-

odic changes in the environment.

A commuter diatom has an unusu-

         ally accurate biological clock, a

consequence of the unrelenting

 (35) environmental pressures to which

it is subjected; any diatoms that do

not burrow before the tide arrives

are washed away.

      This is not to suggest that the

 (40)  period of this biological clock is

immutably fixed.  Biologists have

concluded that even though a

diatom does not rely on the envi-

ronment to keep time, environmental

 (45)  factors—including changes in the

tide’s hydrostatic pressure, salin-

ity, mechanical agitation, and

temperature—can alter the period

of its biological clock according to

 (50)  changes in the tidal cycle.  In short,

the relation between an organism’s

biological clock and its environment

is similar to that between a wristwatch

and its owner:  the owner cannot

 (55)  make the watch run faster or slower,

but can reset the hands.  However,

this relation is complicated in intertidal

dwellers such as commuter diatoms

by the fact that these organisms are

 (60)  exposed to the solar-day cycle as

well as to the tidal cycle, and some-

times display both solar-day and

tidal periods in a single behavior.

Commuter diatoms, for example,

 (65)  emerge only during those low tides

that occur during the day.

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Q33:     

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

             

1. The solar-day cycle makes this behavior less advantageous to the commuter diatoms at certain times of the year.

2. The solar-day cycle makes this behavior somewhat more erratic.

3. The solar-day cycle makes this behavior less important to the survival of the commuter diatoms.

4. 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.

5. Because of the solar-day cycle, this behavior is not expressed at certain times during the 24-hour day.

somiz

文章最后一句: Commuter diatoms, for example,  emerge only during those low tides that occur during the day.

那不意思就是, 这个行为只会在白天出现.   其他时间不出现. -->  at certain times during the 24-hour day