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举一反三
【单选题】沿河观柳时，会发现某些多年的老柳树的树干上有树瘤，树瘤形成的原因是害虫侵害树干，影响了树内韧皮部的运输功能．试从植物运输途径分析树瘤形成的原因（ ）
A.
韧皮部内水分和无机盐的向上运输功能受阻
B.
韧皮部内水分和无机盐的向下运输功能受阻
C.
韧皮部内筛管的向下运输功能受阻
D.
韧皮部内筛管的向上运输功能受阻
【单选题】B The banana "tree" is actually not a real tree. This is because there is no wood in the stem(树干) rising above the ground. The stem is made up of leaves growing very close together, one ...
A.
On the flower stalk.
B.
On the leaves.
C.
On the stem.
D.
On the base of the stem.