4008-125-888
首页>SAT考试备考专区>阅读>sat阅读真题+答案+解析

sat阅读真题+答案+解析

2017-12-12 15:04来源:互联网作者:上海管理员

摘要:题目:Plants, and all other living things, require nitrogen for growth; it is an essential component ofnucleic acids and proteins. Although air is mostly nitrogen, this gaseous form is inaccessible toplants and must be fixed into ammonium to render it biolog

今天上海新航道 小编为大家带来的是关于sat阅读的真题,本题是一道批判思维的选这题。

题目:

Plants, and all other living things, require nitrogen for growth; it is an essential component ofnucleic acids and proteins. Although air is mostly nitrogen, this gaseous form is inaccessible toplants and must be fixed into ammonium to render it biologically relevant. Soil bacteria calledrhizobia fix nitrogen, but to do this they must first take up residence inside the roots oflegumes like pea, alfalfa, clover, and soybean.

Soon after a legume begins to grow, rhizobia invade its root hairs and multiply, causing theplant to form specialized organs—nodules—that contain the proliferating bacteria. Thissymbiotic arrangement benefits both parties: legumes can thrive without nitrogen fertilizersonly if they have functional nitrogen-fixing nodules, while the bacteria receive the energyneeded to multiply and fix nitrogen from the plant. When the plant dies, the fixed nitrogen isreleased into the soil so other plants can use it. This process has significant implications foragriculture, as nitrogen is the most common nutrient deficient in the earth’s soil and, thus,the one most commonly supplied by chemical fertilizers.

Rhizobia are a diverse group taxonomically, genetically, and metabolically. They can be foundin distant genera. Their symbiotic trait appears to have arisen independently multiple times byhorizontal transfer of genes. However, it is not thought that this horizontal gene transferis sufficient to confer symbiosis, or to explain the biodiversity of rhizobia. There must beselective pressures preventing or permitting the expression of the acquired symbiosis trait andadaptive mechanisms to deal with these pressures. But neither the pressures nor themeasures taken to circumvent them are known.

What can reasonably be inferred about the fixed nitrogen released when a plant dies?

A.It is biologically insignificant because it reverts to its gaseous form.

B.It is not sufficient to maintain adequate nitrogen levels in soil.

C.It is less useful for other plants than the nitrogen found in chemical fertilizers.

D.It is not a consideration in farmers' decisions regarding agricultural practices.

上海新航道SAT培训班

答案:B

解析:

Choice B is the best answer. The author states that soil commonly is nitrogen-deficient andthat nitrogen is often supplied by fertilizers, even though the fixed nitrogen released whenlegume plants with nitrogen-fixing nodules die can be used by other plants. This suggests thatthe fixed nitrogen those legume plants release is not enough to supply all of the nitrogen thatis needed in soil; fertilizers are needed to address the remaining nitrogen deficiency.

上海sat'培训班

上海sat'培训班

上海sat'培训班

相关热点: sat解析

免费领取资料

免费领取最新剑桥雅思、TPO、SAT真题、百人留学备考群,名师答疑,助教监督,分享最新资讯,领取独家资料。

方法1:扫码添加新航道老师

微信号:shnc_2018

方法2:留下表单信息,老师会及时与您联系

热门课程

  • SAT考前模考冲刺班
  • 走读班(3-6人)
  • 住宿班(3-6人)
  • SAT一对一
课程名称 班级人数 课时 学费 报名
SAT考前模考冲刺班 40课时 ¥3800 在线咨询
SAT十一特训班 6-8人 48课时 ¥16800 在线咨询
SAT模考刷题班 不限 4天 ¥5800 在线咨询
课程名称 班级人数 课时 学费 报名
SAT强化班(3-6人,走读) 3-6人 64课时 ¥31800 在线咨询
SAT冲刺班(3-6人.走读) 3-6人 32课时 ¥18800 在线咨询
SAT精英班(3-6人,争1500分) 3-6人 48课时 ¥16800 在线咨询
SAT预备班(3-6人,走读) 3-6人 32课时 ¥16800 在线咨询
SAT基础班(3-6人,走读) 3-6人 64课时 ¥30800 在线咨询
课程名称 班级人数 课时 学费 报名
课程名称 班级人数 课时 学费 报名
SAT一对一 1 按需定制 ¥1280元 在线咨询

免责声明
1、如转载本网原创文章,请表明出处;
2、本网转载媒体稿件旨在传播更多有益信息,并不代表同意该观点,本网不承担稿件侵权行为的连带责任;
3、如本网转载稿、资料分享涉及版权等问题,请作者见稿后速与新航道联系(电话:021-64380066),我们会第一时间删除。

  • 徐家汇校区
  • 人民广场校区
  • 浦东校区
  • 中山公园校区
  • 杨浦校区
  • 闵行校区
  • 松江校区
  • 封闭集训营
  • 地址:徐汇区裕德路126号

    乘车路线:地铁1、4号线上海体育馆、3号线9号线宜山路站、11号线上海游泳馆站

  • 地址:南京西路338号天安中心24楼

    乘车路线:地铁1、2、8号线人民广场站

  • 地址:浦东新区世纪大道1128号耀通科技大厦3楼(地铁2号线世纪大道站12号口出)

    乘车路线:地铁2、4、6号线世纪大道站

  • 地址:长宁路1158号 贝多芬广场 A座4楼414室

    乘车路线:乘车路线:地铁3、4号线中山公园站

  • 地址:杨浦区国宾路18号万达广场A座18楼

    乘车路线:地铁10号线五角场站

  • 地址:东川路1779-19号

    乘车路线:地铁5号线 东川路站4号口出

  • 地址:松江大学城四期校区:文汇路928弄想飞天地2204

    乘车路线:地铁9号线松江大学城站下

  • 地址:上海市浦东新区惠南镇拱极路2151号

    乘车路线:地铁16号线惠南站

总部地址:北京市海淀区中关村大街28-1号6层601 集团客服电话:400-097-9266 总部:北京新航道教育文化发展有限责任公司

Copyright © www.xhd.cn All Rights Reserved 京ICP备05069206

  • 微信公众号
  • 微信社群