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.
答案是A，我选了D。看了以前大家的讨论，天哪，连解释也没看懂，5555。 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。 为什么非A--->非B是加强呢？从来没听说过也？  | 
