题目
单选题请阅读下面材料，完成小题。 There is evidence that the usual variety of high blood pressure is，in part，a familiar disease．Since families have similar genes as well as similar environments，familiar diseases could be due to shared genetic influences，to shared environmental factors，or to both．For some years，the role of one environmental factor commonly shared by families，namely dietary salt(i．e．sodium chloride)，has been studied at Brook haven National Laboratory．These studies suggest that chromic excess salt ingestion can lead to high blood pressure in man and animals．Some individuals，however，and some rats consume large amounts of salt without developing high blood pressure．No matter how strictly all environmental factors were controlled in these experiments，some salt-fed animals never developed hypertension whereas a few rapidly developed very severe hypertension followed by early death．Thesemarked variations were interpreted to result from differences in genetic constitution． By mating is successive generations only those animals that failed to develop hypertension from salt ingestion，a resistant strain(the“R”strain)has been evolved in which consumption of large quantities of salt fails to influence the blood pressure significantly．In contrast，by mating only animals that quickly develop hypertension from salt，a sensitive strain(the“S”strain)has also been developed． The availability of these two strains permits investigations not heretofore possible．They provide a plausible laboratory model on which to investigate some clinical aspects of the human prototypes of hypertension．More important，there might be the possibility of developing methods by which genetic susceptibility of human beings to high blood pressure can be defined without waiting for its appearance.Radioactive sodium 22 was an important“tool”in working out the characteristics of the sodium chloride metabolism． The study of the effects of salt on high blood pressure was carried out_________. A．as members of the same family tend to use similar amounts of salt B．to explore the long—term use of a sodium based substance C．because it was proven that salt caused high blood pressure D．because of the availability of chemically pure salt and its derivatives
单选题
请阅读下面材料，完成小题。
There is evidence that the usual variety of high blood pressure is，in part，a familiar disease．Since families have similar genes as well as similar environments，familiar diseases could be due to shared genetic influences，to shared environmental factors，or to both．For some years，the role of one environmental factor commonly shared by families，namely dietary salt(i．e．sodium chloride)，has been studied at Brook haven National Laboratory．These studies suggest that chromic excess salt ingestion can lead to high blood pressure in man and animals．Some individuals，however，and some rats consume large amounts of salt without developing high blood pressure．No matter how strictly all environmental factors were controlled in these experiments，some salt-fed animals never developed hypertension whereas a few rapidly developed very severe hypertension followed by early death．These
marked variations were interpreted to result from differences in genetic constitution．
By mating is successive generations only those animals that failed to develop hypertension from salt ingestion，a resistant strain(the“R”strain)has been evolved in which consumption of large quantities of salt fails to influence the blood pressure significantly．In contrast，by mating only animals that quickly develop hypertension from salt，a sensitive strain(the“S”strain)has also been developed．
The availability of these two strains permits investigations not heretofore possible．They provide a plausible laboratory model on which to investigate some clinical aspects of the human prototypes of hypertension．More important，there might be the possibility of developing methods by which genetic susceptibility of human beings to high blood pressure can be defined without waiting for its appearance.
Radioactive sodium 22 was an important“tool”in working out the characteristics of the sodium chloride metabolism．
The study of the effects of salt on high blood pressure was carried out_________.
There is evidence that the usual variety of high blood pressure is，in part，a familiar disease．Since families have similar genes as well as similar environments，familiar diseases could be due to shared genetic influences，to shared environmental factors，or to both．For some years，the role of one environmental factor commonly shared by families，namely dietary salt(i．e．sodium chloride)，has been studied at Brook haven National Laboratory．These studies suggest that chromic excess salt ingestion can lead to high blood pressure in man and animals．Some individuals，however，and some rats consume large amounts of salt without developing high blood pressure．No matter how strictly all environmental factors were controlled in these experiments，some salt-fed animals never developed hypertension whereas a few rapidly developed very severe hypertension followed by early death．These
marked variations were interpreted to result from differences in genetic constitution．
By mating is successive generations only those animals that failed to develop hypertension from salt ingestion，a resistant strain(the“R”strain)has been evolved in which consumption of large quantities of salt fails to influence the blood pressure significantly．In contrast，by mating only animals that quickly develop hypertension from salt，a sensitive strain(the“S”strain)has also been developed．
The availability of these two strains permits investigations not heretofore possible．They provide a plausible laboratory model on which to investigate some clinical aspects of the human prototypes of hypertension．More important，there might be the possibility of developing methods by which genetic susceptibility of human beings to high blood pressure can be defined without waiting for its appearance.
Radioactive sodium 22 was an important“tool”in working out the characteristics of the sodium chloride metabolism．
The study of the effects of salt on high blood pressure was carried out_________.
A．as members of the same family tend to use similar amounts of salt
B．to explore the long—term use of a sodium based substance
C．because it was proven that salt caused high blood pressure
D．because of the availability of chemically pure salt and its derivatives
题目解答
答案
参考答案：A
推理判断题。由第一段第二、三句话可知，家庭成员的生活环境相同，因此摄入的食盐量也相同，可以用来研究摄人食盐对高血压的影响，故选A。
解析
考查要点：本题主要考查学生对材料主旨的理解能力，以及根据上下文进行合理推断的能力。
解题核心：需明确研究盐与高血压关系的根本目的，即材料中提到的“家庭共享环境因素”这一关键点。
破题关键：抓住材料中“familiar diseases could be due to shared environmental factors”和“dietary salt as a commonly shared environmental factor”等信息，理解研究盐摄入量的目的是为了分析家庭环境中共同因素对疾病的影响。
材料主旨：研究盐摄入对高血压的影响，旨在通过家庭共享的环境因素（如盐摄入量），探讨遗传与环境在高血压中的作用。
选项分析：
- A：正确。材料强调家庭成员盐摄入量相似，因此研究盐作为共享环境因素的作用。
- B：错误。材料未提及“长期使用钠基物质”的探索目标。
- C：错误。材料中盐与高血压的因果关系尚未被“证明”，仅是“可能”相关。
- D：错误。纯盐的可用性并非研究目的，而是实验工具（如放射性钠）的说明。