SAT官方阅读每日一练 18年5月22日

2018年05月22日19:47 来源：小站整理: 参与（0）阅读（6077）

摘要：5月SAT考试已结束，而下一场考试远在10月，相信很多人还在苦闷的备考期吧。由SAT考试官方出品，每天一道权威SAT阅读练习题，是放松身心的绝佳调剂资料。本文为大家带来年5月22日sat阅读练习题，属于考词义辨析题，需要读懂上下文，并排除掉干扰项pertineent，难度较大。每天一小道，考试更健康。

为广大SATer带来2018年5月22日的SAT阅读每日一练，考察篇章层面的结构题，需要通读全文并理解作者行文架构，难度较大。配有答案，解析，众考生，慢慢操练吧。文末附2018SAT阅读题型清单。

SAT阅读每日一练

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.