问题
单项选择题
色素上皮参与视紫红质光化学反应的主要环节是（）
A.生色基团与视蛋白的分离
B.生色基团与视蛋白的结合
C.视黄醛由顺型异构为全反型
D.视黄醛由全反型异构为顺型
E.以维生素A即时合成视紫红质
答案
参考答案：D
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色素上皮参与视紫红质光化学反应的主要环节是（）
A.生色基团与视蛋白的分离
B.生色基团与视蛋白的结合
C.视黄醛由顺型异构为全反型
D.视黄醛由全反型异构为顺型
E.以维生素A即时合成视紫红质
参考答案：D
阅读下列短文，从文后各题所给的四个选项中选出一个最佳答案。 Hundreds of years ago in a small town, a moneylender lent a lot of money to a poor man. The moneylender , who was old and ugly, _____ the poor man’s beautiful daughter. So he came up with an idea. He said the poor man didn’t need to return the money to him _____ he could marry his daughter. Both the man and his daughter were________. The moneylender then told them that he would put a small _______ stone and a small white stone into an empty bag. The girl would have to ______ one. If she took the black stone , she would become the moneylender’s _______ and her father’s debt would be let go. If she picked the white stone, she didn’t need to marry him and her father’s debt would______ be let go. Her father would be put into prison if she refused to pick a stone. As they talked, the moneylender picked up two stones. As he did that, the girl______that he had put two black stones in the bag. He then asked the girl to pick her stone from the bag. The girl thought for a while and then had an idea. She put her hand into the bag and took out a stone. ______ looking at it, she let it fall onto the path where it ______ became lost among all the other stones. “ Oh how______ I was！” She said, “But never ______. If you look into the bag for the one that is left, you will be able to _______ which stone I picked.” This ______ tells: Sometimes we can think about things in a _______way. Most difficult problems do have an solution.
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