During the traditional wedding ceremony, the
CD#6bridal couple promises each other lifelong 【M1】______
devotion. Yet, about one out of four American
marriages ends in divorce. Since 1940, the
divorce rate has more than doubled, and
experts predict that, of all marriages that
occured in the 1970s, about【M10】% will end in 【M2】______
divorce. The USA is one of the highest divorce 【M3】______
rates in the world, perhaps even the highest.
What goes wrong? That fact that divorce is so
common in the United States does not mean that
Americans consider marriage a casual, unimportant
relationship. Just opposite is true. Americans 【M4】______
expect a great deal from marriage. They seek physical
, emotional, and intellectual compatibility.
They want to be loved deep and understood. It 【M5】______
is because Americans expect so much from
marriage that so many get divorce. They prefer 【M6】______
no marriage at all to a marriage without love
and understanding. Which typical American
optimist, they end one marriage in the 【M7】______
hope of that the next will be happier. With 【M8】______
no fault divorce laws in many states, it is
easier than never to get a divorce. Some American 【M9】______
women stay in unhappy marriages because they
do not have the education or job experience
to support themselves and their children.
But most American women believe that, ff necessary,
they can make it lonely without a 【M10】______
husband. All things considered, Americans
have little reason to continue an unhappy
marriage.
【M1】
第1题
从一组酸性强弱不同的游离黄酮混合物的乙醚溶液中,用pH梯度萃取法萃取分离7-OH黄酮,多选用
A.5%碳酸氢钠溶液
B.5%碳酸钠溶液
C.0.2%氢氧化钠溶液
D.4%氢氧化钠溶液
E.5%盐酸溶液
第2题
在用pH梯度萃取法分离酸性强弱不同的黄酮苷元时,能溶于5%.NaHCO3溶液的化合物是
A.7,4′-二羟基黄酮
B.7-羟基黄酮
C.2′-羟基黄酮
D.5-羟基黄酮
E.4′-羟基黄酮
第3题
pH梯度萃取法分离酸性不同的游离黄酮时,5%碳酸氢钠水溶液可萃出的是
A.7,4’-二羟基黄酮
B.5.羟基黄酮
C.4’-羟基二氢黄酮
D.6-羟基黄酮
E.7-羟基黄酮
第4题
pH梯度萃取法分离游离黄酮时,用5%碳酸氢钠水溶液萃取,可得到
A、7,4′-二羟基黄酮
B、7-羟基黄酮
C、4′-羟基黄酮
D、5-羟基黄酮
E、3-羟基黄酮
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