更多“黄斑中心小凹处有哪种细胞？（）”相关的问题
Diseases of Agricultural Plants Plants, like animals, are subject to diseases of various kinds. It has been estimated that some 30,000 different diseases attack our economic plants; forty are known to attack corn, and about as many attack wheat. The results of unchecked plant disease are all too obvious m countries which have marginal food supplies. The problem will soon be more widespread as the population of the world increases at its frightening rate. Even in countries which are now amply fed by their agricultural products there could soon be critical food shortages. It is easy to imagine the consequences of some disastrous attack on one of the major crops; the resulting famines could kill millions of people, and the resulting hardship on other millions could cause political upheavals disastrous to the order of the world. Some plants have relative immunity to a great many diseases, while others have a susceptibility to them. The tolerance of a particular plant changes as the growing conditions change. A blight may be but a local infection easily controlled; on the other hand it can attack particular plants in a whole region or nation. An example is the blight which killed virtually every chestnut tree in North America. Another is the famous potato blight in Ireland in the last century. As a result of that, it was estimated that one million people died of starvation and related ailments. Plant pathologists have made remarkable strides in identifying the pathogens of the various diseases. Bacteria may invade a plant through an infestation of insect parasites carrying the pathogen. A plant can also be inoculated by man. Other diseases might be caused by fungus which attacks the plant in the form of a mold or smut or rust. Frequently such a primary infection will weaken the plant so that a secondary infection may result from its lack of tolerance. The symptoms shown may cause an error in diagnosis, so that treatment may be directed toward bacteria which could be the result of a susceptibility caused by a primary virus infection.
A. Some plants have relative immunity to a great many diseases, while others have a susceptibility to them.B. The tolerance of a particular plant changes as the growing conditions change.C. A blight killed virtually every chestnut tree in North America.D. A blight may be a national infection.
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按材料结构属性划分，下列不属于高分子材料的是（）
A.涂料
B.橡胶
C.陶瓷
D.合成塑料
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大气环境影响预测方案的设计，关键因素是（）。
A.选择污染源及其排放方案
B.确定污染源的预测因子
C.拟建项目污染治理方案的设计
D.合理选择污染源的组合方案
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自适应自动舵与普通自动舵比较，其主要优点是（） ①自动确定各项系数； ②进行最佳控制； ③减少操舵次数和舵角。
A.①～③
B.①②
C.①③
D.②③
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影响甲烷转化反应平衡的因素有哪些
A. 催化剂活性 B. 水碳比 C. 温度 D. 压力
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在自然界，没有上，就无所谓下；在社会中，没有先进，就无所谓落后；在认识中，没有正确，就无所谓错误。这说明______。
A.矛盾双方是相互排斥的
B.矛盾双方是相互渗透的
C.矛盾双方是相互依存的
D.矛盾双方是相互转化的
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在Foxbase中，最多可同时打开10个数据库文件。（）
A . 正确
B . 错误
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经业务会计档案保管机构批准，调阅人在业务会计档案保管人员陪同下调阅，可以（）业务会计档案。
A.借调
B.抄录
C.复印
D.复制
E.打印
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下列关于存储器的叙述中,正确的是( )
A. PC可以配置任意多的内存条 B. PC中的存储器都是半导体存储器 C. 插在主板内存槽上的内存条由闪存芯片组成 D. 采用存储器层次结构的目的是为了达到性能/价格比的优化
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下列（ ）情形，注册会计师可能不对应收账款实施函证。
A.应收账款金额为很小，但交易频繁 B.根据审计重要性原则，有充分证据表明应收账款对财务报表不重要 C.函证费用过高 D.注册会计师认为函证很可能无效
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货物损失调查和赔偿材料分别由定责单位、责任单位和办理赔偿单位完整打印并加盖货物损失处理专用章或单位公章后保存，自结案的次年1月1日起，保管（）年。
A.1 B.2 C.3 D.4
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由于电子表格能够非常容易进行修改，并可能缺少控制活动，因此电子表格往往面临重大固有风险和错报，这些固有风险和错误情况可能包括( )。
A．与其他系统传输数据时产生的错误
B．由错误数据录入、错误引用或其他简单的剪贴功能造成的错误
C．单元格范围定义不当、单元格参考错误或电子表格链接不当
D．创建错误的公式从而产生了错误的结果
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世界上种类最多，数量最多的动物是（）。
A.鸟类 B.哺乳动物 C.爬行动物 D.昆虫
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网上增发新股可以采用网上发行和网下发行，网上增发新股申购的一般操作程序与新股网上
A．正确B．错误C．放弃
B．错误C．放弃
C．放弃
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