题目内容
木材的构造可分为（）与（）？
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木材构造决定着木材的实用性与装饰性
材横断面上的同心环，称之为髓线
[音频]BananasRecently, some concerns have been ___1____ about the health of the world's banana plants. A number of __2_____reports have said that bananas may _____3_______ disappear. Some ___4____ that this could happen in as little as ten years.Bananas are one of the world’s most important food____5___. They are also the fourth most____6_____ export. Bananas do not grow from seeds. Instead, they grow from existing plants. Bananas are _____7______ by disease because all the plants on a farm are __8____ of each other. They all share the same genetic weaknesses.The International Network for the Improvement of Banana and Plantain supports ____9_____ on bananas. The group has ______10________ in France and other offices in the major banana- growing areas of the world. The group says that more research must be done to develop ___11______ kinds of bananas.The UN agency says farmers should grow different kinds of bananas. This __12______ against diseases that __13____ only one kind. Experts warn that disease may cause the Cavendish banana to disappear. This has already ___14_______ to one popular banana because of its genetic weakness against disease.
M2M按照通信对象分类不包含下列哪一项（）。
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