2016年5月10日SAT考试阅读题

今天为大家带来2016年5月10日SAT考试阅读题附答案和解析，希望可以帮助到考生们。

SAT考试阅读题目Critical Reading>Select an Answer

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

　　Soon after a legume begins to grow, rhizobia invade its root hairs and multiply, causing the plant to form specialized organs—nodules—that contain the proliferating bacteria. This symbiotic arrangement benefits both parties: legumes can thrive without nitrogen fertilizers only if they have functional nitrogen-fixing nodules, while the bacteria receive the energy needed to multiply and fix nitrogen from the plant. When the plant dies, the fixed nitrogen is released into the soil so other plants can use it. This process has significant implications for agriculture, 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 found in distant genera. Their symbiotic trait appears to have arisen independently multiple times by horizontal transfer of genes. However, it is not thought that this horizontal gene transfer is sufficient to confer symbiosis, or to explain the biodiversity of rhizobia. There must be selective pressures preventing or permitting the expression of the acquired symbiosis trait and adaptive mechanisms to deal with these pressures. But neither the pressures nor the measures taken to circumvent them are known.

　　The underlined word "relevant" most nearly means __________

　　(A) connected.

　　(B) linked.

　　(C) useable.

　　(D) pertinent.

　　答案：C

　　解析：

　　Choice C is the best answer. The author states that the gaseous form of nitrogen "is inaccessible to plants and must be fixed into ammonium to render it biologically relevant." In this context, "relevant" most nearly means "useable." The author’s point is that the nitrogen must be in a form that is biologically useable or accessible to plants.

    欲了解更多有关雅思、托福、省考、SAT等语言类考试及培训类课程，欢迎拨打温哥华环球教育官方学校的咨询电话：604-285-2928或778-986-7029；或访问温哥华环球教育唯一官方网站http://vancouver.gedu.org；

    同时您也可以扫描加拿大环球教育官方微信二维码，与雅思大神级名师互动问答，为您的考试保驾护航。