19. Black Americans are, on the whole, about twice as likely as White Americans to develop high blood pressure. This likelihood also holds for westernized Black Africans when compared to White Africans.
Researchers have hypothesized that this predisposition in westernized Blacks may reflect an interaction between western high-salt diets and genes that adapted to an environmental scarcity of salt.
Which of the following statements about present-day, westernized Black Africans, if true, would most tend to confirm the researchers’ hypothesis?
(A) The blood pressures of those descended from peoples situated throughout their history in Senegal and Gambia, where salt was always available, are low.
(B) The unusually high salt consumption in certain areas of Africa represents a serious health problem.
(C) Because of their blood pressure levels, most White Africans have markedly decreased their salt consumption.
(D) Blood pressures are low among the Yoruba, who, throughout their history, have been situated far inland from sources of sea salt and far south of Saharan salt mines.
(E) No significant differences in salt metabolism have been found between those people who have had salt available throughout their history and those who have not.
why A?
但是D也是-A->-B
D有两个问题:
1. 这里有个遗传的问题, D未涉及到.
2. D是 -A --> Ｂ而不是不是 -B: 历史上远离盐, 但是BLOOD PRESSURE 依然底, 所以反而起反对的作用.
望指教.
懂了！
一直不懂，什么叫White Africans？？
Black Africans 是啥？？
脸红下……
black africans就是非洲黑人啊
white africans就是非洲白人，比如北非，埃及人啊什么的
他们虽然黑，但是是属于白色人种
還是不懂為何(A)是 -B --> -A
A1: high-salt diet + A2: genes
B: high blood pressure
(A) The blood pressures of those descended from peoples situated throughout their history in Senegal and Gambia,
-B A2
where salt was always available, are low.
+A1
所以應該是 -B ---> +A1
這樣怎會support???
the author hypothesized that A led to B ,
A : western high-salt diets + genes that adapted to an environmental scarcity of salt.
B: high blood pressure
the answer A argue that :
-A : those descended from peoples situated throughout their history in Senegal and Gambia (imply low-salt diets)+ salt was always available
-B:pressure of blood is low
are you clear ?
我想明白了,不用回答我的问题了.
只有逆否命题和原命题等价吧 (A->B <=> -B->-A)
请知道的XDJM们可否告知A,B代表的具体情况, 可具体讨论之.
谢谢!
不好意思, 忘了看下面的了. (浏览器有问题)
不用回答了.
but "-A" should be those descended from peoples situated throughout their history in Senegal and Gambia (imply low-salt diets)+ genes that adapted to an environmental not scarcity of salt
so the issue is that "genes" doesn't appear in (A), then how can it support?
so the issue is that "genes" doesn't appear in (A), then how can it support?
those descended from peoples situated throughout their history 这句话里面不是暗含了基因的因素吗。
A说现在西化的非洲S和G人，他们从祖先到现在都适应了有盐的环境，现在即使是高盐的环境，而且血压也不高。
原文说的是，西化的非洲人，历史上适应了缺盐的环境，现在吃高盐的食物，血压就高。
形成A--->B
那么非A--->非B加强。
只有逆否命题和原命题等价吧 (A->B <=> -B->-A)
请知道的XDJM们可否告知A,B代表的具体情况, 可具体讨论之.
谢谢!
非常的晕为什么A -> B here is: -A -> -B
又想了一次，还是不明白为什么The affirmative pattern for the argument A -> B here is: -A -> -B，不是应该逆否命题才能推出原命题吗？
5555555555555，
到底是怎么回事呀？
哪位ＮＮ帮忙解释一下喽！
再顶一下
“形成A--->B
那么非A--->非B加强。”
是这样呢？
还是想不明白这题的逻辑关系
NN来解释阿
lawyer在哪儿啊啊啊啊
只有逆否命题和原命题等价吧 (A->B <=> -B->-A)
请知道的XDJM们可否告知A,B代表的具体情况, 可具体讨论之.
谢谢!
非常的晕为什么A -> B here is: -A -> -B
我也有这个疑问.是否逆否命题和否命题都可以作加强作用呢?
偶的理解：欢迎讨论。这是道异因异果的加强。
结论是“基因中缺盐，血压高”
加强选项就是“基因中不缺盐，血压低”
D是削弱，“基因中缺盐，但血压也不高”，同因异果的削弱。
当然有些说法是换词表达，可能造成点障碍，比如“祖辈”就是指基因的因素。
还有：加强和削弱只需要部分地支持，或是反对就行，不用像假设那么严格，假设只是最严格意义上的加强或削弱
偶的理解：欢迎讨论。这是道异因异果的加强。
结论是“基因中缺盐，血压高”
加强选项就是“基因中不缺盐，血压低”
D是削弱，“基因中缺盐，但血压也不高”，同因异果的削弱。
当然有些说法是换词表达，可能造成点障碍，比如“祖辈”就是指基因的因素。
还有：加强和削弱只需要部分地支持，或是反对就行，不用像假设那么严格，假设只是最严格意义上的加强或削弱
so the issue is that "genes" doesn't appear in (A), then how can it support?
those descended from peoples situated throughout their history 这句话里面不是暗含了基因的因素吗。
A说现在西化的非洲S和G人，他们从祖先到现在都适应了有盐的环境，现在即使是高盐的环境，而且血压也不高。
原文说的是，西化的非洲人，历史上适应了缺盐的环境，现在吃高盐的食物，血压就高。
形成A--->B
那么非A--->非B加强。
这个讲的最清楚，我没学过 a-b。这是一个interaction effect, 2个因素分别是环境含盐情况和是否适应含盐环境，搭配起来就是：高含盐环境， 不适应得人，血压高（题设）；高含盐环境，适应的人， 则血压低 （推出）； 至于低含盐状况，题目没讲。
理解题意了就对了。
楼上的兄弟解释的非常准确.
这题我一开始以为是在说"吃的盐越多,越容易得高血压",结果错选了D.
而实际上,该题说的是"因(基因)长期适应低盐环境,那些黑人刚到高盐份地区,会因为不适应而得高血压",焦点在"适应性和高血压得关系".
A正说明了那些人由于长期生存在高盐环境,基因已经适应了,故不再容易得高血压了.
至于D,焦点在盐份含量与高血压的关系,已经离题了.
充分必要问题：
画图解释就清楚了：
题目意思是：Consumption: high Gene: low => Blood Pressue: high (3个量的关系)
A: Consumption: high Gene: high => Blood Pressue: low (一个变量取反，应变量自然相反)
D: Consumption: low Gene: low => Blood Pressue: low (两个变量同时取反，根据一般数学原理无法导出应变量的变化，所以D不对)
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