单项选择题

Which of the following statements about ice-nucleating-active bacteria is true

A．They may cool the grain to - 10℃.
B．They can weaken the beetles' resistance to coldness.
C．They can be grown on most plant leaves.
D．They are used only in biological researches.
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单项选择题
We learn from the passage that ______.
A．the bacteria are only effective against three species of beetles
B．Fields' technique is less effective in winter
C．Fields' technique may kill nearly all the beetles at -10℃
D．Insects may develop resistance against the bacteria
单项选择题
Before the 17th century, the little people or the hidden people were ______.
A．highly respected
B．called universally as fairies
C．believed to be active at night
D．said to move about naked all the time
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