[单项选择]

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In an intact plant community, undisturbed by human intervention, the composition of a community is mainly a function of the climate and the type of soil. Today, such original communities are very rare—they are practically limited to national parks and reservations. Civilization has progressively transformed the conditions determining the composition of plant communities. For several thousand years vast areas of arable land have been hoed, ploughed, harrowed and grassland has been cut or grazed. During the last decades the use of chemical substances, such as fertilizers and most recently of weed killers (herbicides) has greatly influenced the composition of weed communities in farm land. All selective herbicides have specific ranges of activity. They control the most important weeds but not all th A. depends on climate and soil type in a virgin environment undamaged by human beings B. was greatly affected by human beings before they started using chemical substances on the soil C. was radically transformed by uncivilized human beings D. refers to plants, trees, climate, type of soil and the ecological environment 查看答案 更多"{{B}}TEXT C{{/B}} In an"的相关试题: [单项选择] {{B}}TEXT C{{/B}} In an intact plant community, undisturbed by human intervention, the composition of a community is mainly a function of the climate and the type of soil. Today, such original communities are very rare—they are practically limited to national parks and reservations. Civilization has progressively transformed the conditions determining the composition of plant communities. For several thousand years vast areas of arable land have been hoed, ploughed, harrowed and grassland has been cut or grazed. During the last decades the use of chemical substances, such as fertilizers and most recently of weed killers (herbicides) has greatly influenced the composition of weed communities in farm land. All selective herbicides have specific ranges of activity. They control the most important weeds but not all th A. Because they cannot be eradicated by herbicides. B. Because all selective herbicides can encourage the growth of previously unimportant weeds by eliminating their competitors. C. Because they were hardly considered before so that their seeds were not prevented from germinating. D. Because they benefit greatly from the fertilizer applied to the farm land. 查看答案 [单项选择]In an intact plant community, undisturbed by human intervention, the composition of a community is mainly a function of the climate and the type of soil. Today, such original communities are very rare—they are practically limited to national parks and reservations. Civilization has progressively transformed the conditions determining the composition of plant communities. For several thousand years vast areas of arable land have been hoed, ploughed, harrowed and grassland has been cut or grazed. During the last decades the use of chemical substances, such as fertilizers and most recently of weed killers (herbicides) has greatly influenced the composition of weed communities in farm land. All selective herbicides have specific ranges of activity. They control the most important weeds but not all the plants of a community. The latter profit from the new free space and from the fertilizer as much as the crop does; hence they often spread rapidly and become weeds unless anothe A. depends on climate and soil type in a virgin environment undamaged by human beings B. was greatly affected by human beings before they started using chemical substances on the soil C. was radically transformed by uncivilized human beings D. refers to plants, trees, climate, type of soil and the ecological environment 查看答案 [填空题] A．German B．region C．plant D．sufficient 查看答案 我来回答: 提交 最新试题 ●    [判断题]金信优E贷可用于支付购房贷款首付款 ●    制造商自组销售队伍的原因是（）。 ●    [单选题]用水或一般灭火器浇灭离接触网带电部分不足（ ）的燃着物体时，接触网必须停电 ●    [单选题]在线性编辑中会出现断磁现象的是（）。 ●    在资产负债表中，如果交易性金融资产的公允价值低于其账面价值，应按照差额调整交易性金融资产的账面价值， ●    《继电保护和安全自动装置基本试验方法》规定，当测量时间大于1s时，相对误差不大于（）。 网站地图 我要搜题网  版权所有  ©2023  湘ICP备18016427号   购买搜题卡查看答案 [会员特权] 开通VIP， 查看 全部题目答案 [会员特权] 享免全部广告特权 推荐91天 ¥36.8 ￥80元 31天 ¥20.8 ￥40元 365天 ¥88.8 ￥188元 请选择支付方式 微信支付 支付宝支付 点击支付即表示同意并接受了《购买须知》 立即支付 系统将自动为您注册账号 已有账号登录 找回账号密码 请使用微信扫码支付 订单号： 请不要关闭本页面，支付完成后请点击【支付完成】按钮 支付完成 取消支付 恭喜您，购买搜题卡成功 系统为您生成的账号密码如下： 账号 密码 重要提示：请拍照或截图保存账号密码！ 我要搜题网官网：https://www.woyaosouti.com 我已记住账号密码