第8 题

　　In this passage RDAs refers to ______.

　　A types of vitamins B types of protein C types of minerals D amounts of energy, protein, vitamins, and minerals

　　【正确答案】：D

　　【答案解析】 [分析] 细节题型。见文章第三句： RDAs are suggested amounts of calories, protein, and some minerals and vitamins for an adequate diet.选项 D 正确，选项 A、B、C 都不全面。

　　第9题

　　One implication in this passage is that ______.

　　A all RDAs have been established B not all RDAs have been established yet C it's not important to know RDAs D RDAs are necessary only for sick people

　　【正确答案】：B

　　【答案解析】[分析] 推断题型。 见文章第二句：These are known as the Recommended Dietary Allowances(RDAs)and are updated regularly based on new research in 模考吧 www.mokaoba.com nutrition.可知 RDAs 要经常更新，所以选项A不对，选项C、D也披排除：只有选项 B 正确。

　　第10 题

　　The reduction of calories in the diet is particularly good for people who suffer from ______.

　　A obesity B premature heart disease and diabetes C high blood pressure and cholesterol levels D all of the above

　　【正确答案】：D

　　【答案解析】 [分析] 细节题型。 见第一段最后一句：These suggestions are especially appropriate for people who have other factors for chronic diseases due to family history of obesity，premature heart disease, diabetes, high blood pressure, and high blood cholesterol, or for those who use tobacco.选项 A、B、C 三个 选项都提及到，但只有选项 D 最全面，所以 D 正确。

　　第11题 The most popular organic gem is the pearl. A pearl is the response of a marine mollusk to the presence of an irritating impurity accidentally introduced into its body; a cultured pearl is the result of the intentional insertion of a mother-of-pearl bead into a live mollusk. Whether introduced accidentally or intentionally, the pearl-making process is the same: the mollusk coats the irritant with a substance called nacre. Nacre is composed chiefly of calcium carbonate. Because very few natural pearls are now on the market, most pearls used in free jewelry are cultured. These include "Biwa" pearls and most other freshwater pearls. Cultured pearls are not easily distinguished from natural pearls except by an expert. Which of the following people could tell the difference between a cultured pearl and an organic pearl?

　　A Scuba diver. B Fisherman. C Jeweler. D Clerk.

　　【正确答案】：C 【答案解析】 [分析] 细节题型。 见文章最后一句：Cultured pearls are not easily distinguished from natural pearls except by an expert.只有专家才能区分出天然珍珠和人工培 育的珍珠。珠宝商当然应是这类专家，所以选项 C 正确。A.Scuba diver 戴水 肺的潜水员 B.Fisherman 渔民和 D.Clerk 职员当然不是鉴别珠宝的行家了。

　　第12 题

　　What is the chief component of nacre?

　　A Sand. B Bead. C Calcium carbonate. D Biwa.

　　【正确答案】：C

　　【答案解析】 [分析] 细节题型。 见文章第四句：Nacre is composed chiefly of calcium carbonate.选项 C.Calcium carbonate(碳酸钙)正确。

　　第13题 The difference between a pearl and a cultured pearl is the nature of the ______.

　　A color B introduction of the irritating impurity C coating material D irritating impurity

　　【正确答案】：B

　　【答案解析】 [分析] 细节题型。 文章第二句(A pearl is the response of a marine„a live mollusk. ) 指出：天然珍珠中的刺激性的杂物是偶然进入体内的(accidentally introduced into its body);而人工培育的珍珠中的杂物是人为加入的(the intentional insertion);所以选项 B 正确。

　　第14题 Nacre is a substance that is ______.

　　A mechanically manufactured B the result of laboratory testing C organically secreted by the mollusk D present in the chemical composition of freshwater pounds

　　【正确答案】：C

　　【答案解析】 [分析] 推断题型。 文中第三句(Whether introduced accidentally or intentionally, the pearl-making process is the same: the mollusk coats the irritant with a substance called nacre.)说明无论是天然珍珠还是人工：养殖的珍珠，它们 的形成过程是一样的：贝类用一种被称之为珍珠质的物质将刺激性的杂物包裹 住。由此推断出珍珠质 nacre 是贝类 the mollusk 滋生分泌出的，所以选项 C 正确。

　　第15题 The main idea in this passage is that ______.

　　A most marketable pearls are cultured because nature does not produce enough of its own to satisfy the market B cultured pearls are of a higher quality than natural pearls

　　C there are two major methods of pearl-making D a natural "drought" of pearl production is taking place

　　【正确答案】：C

　　【答案解析】 [分析] 主旨题型。 阅读全文可知本文介绍了珍珠有天然和人工养殖两种形成方式，所以选项 C 正确。