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【多选题】
香蕉枯萎病难以防控的主要原因是( )。
A.
病菌为土壤习居菌，可在土壤存活时间较长。
B.
病原菌侵染寄主后产生分生孢子在植株内传播，并堵塞阻塞导管和筛管。
C.
在侵染早期，症状表现不明显或不表现。
D.
病原菌可通过雨水、灌溉、线虫、耕作、种苗调运等方式传播。
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参考解析：
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【单选题】An elm in our backyard（7）the blight (枯萎病) this summer and dropped stone dead, leafless, almost overnight. One weekend（8）was a normal-looking elm, maybe a little bare in spots but（9）alarming, and the n...
A.
There are so many new books about dying that there are now special shelves set aside for them in bookshops, along with the health-diet and home-repair paperbacks. Some of them are so（1） with detailed information and step-by-step instructions for performing the function, that you’d think this was a new sort of（2）which all of us are now required to learn. The strongest impression the casual reader gets is that proper dying has become an extraordinary,（3）an exotic experience, something only the specially trained can do.
B.
（4）, you could be led to believe that we are the only（5）capable of being aware of death, and that when the rest of nature is experiencing the life cycle and dying, one generation after（6）, it is a different kind of process, done automatically and trivially, or more "natural", as we say.