How many theories does the author mention? According to the passage, why does water travel through plants in unbroken columns?

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问题 How many theories does the author mention?
According to the passage, why does water travel through plants in unbroken columns?

选项 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.