The most important ion in controlling the movement of water into and out of the guard cells is

A. carbon.
B. hydrogen.
C. potassium.
D. nitrogen.
E. sodium.


Answer: C

Biology & Microbiology

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The highest elevation at which trees can grow is

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When a scientist sees patterns among a number of isolated facts, 

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Which of the following scientists proposed that geologic change occurred gradually due to small changes accumulating over long periods of time?

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