单项选择题

The passage answers which of the following questions

A．What is the effect of atmospheric pressure on foliage
B．When do dead cells harm plant growth
C．How does water get to the tops growth
D．Why is root pressure weak

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单项选择题

How do botanists know that root pressure is not the only force that moves water in plants

A．Some very tall trees have weak root pressure.
B．Root pressures decrease in winter.
C．Plants can live after their roots die.
D．Water in a plant's roots is not connected to water in its stem.

单项选择题

According to the passage, why does water travel through plants in unbroken columns

A．Root pressure moves the water very rapidly.
B．The attraction between water molecules is strong.
C．The living cell of plants push the water molecules together
D．Atmospheric pressure supports the columns.