问题
选择题
如用模拟细胞质基质成分的溶液分别培养离体的线粒体和叶绿体，控制光和氧气，如图所示。其中甲、丙表示线粒体，乙、丁表示叶绿体；甲、乙有光照但不供氧气，丙、丁有氧气但在黑暗中。一段时间后，溶液中pH最高和最低的依次是
[ ]A．甲和丁
B．丁和甲
C．丙和乙
D．乙和丙
答案
答案：D
[ ][ ]
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如用模拟细胞质基质成分的溶液分别培养离体的线粒体和叶绿体，控制光和氧气，如图所示。其中甲、丙表示线粒体，乙、丁表示叶绿体；甲、乙有光照但不供氧气，丙、丁有氧气但在黑暗中。一段时间后，溶液中pH最高和最低的依次是
[ ]A．甲和丁
B．丁和甲
C．丙和乙
D．乙和丙
答案：D
In the past, man did not have to think about the protection of his environment. There were few people on the earth, and natural 36 seemed to be unlimited. Today things are 37 . The world has become too 38 . We are 39 our natural resources too quickly, and at the same time we are 40 our environment with dangerous chemicals. If we 41 to do this, human life on earth will not 42 . People realize today that if too many 43 are taken from the sea, there will soon be none left. Yet, with modern fishing 44 , more and more fish are caught. We know that if too many trees are cut down, 45 will disappear and nothing will 46 on the land. Yet, we continue to use bigger and more powerful machines to 47 more and more trees. We realize that if rivers are polluted with waste products from factories, we will die. 48 , in most countries waste products are still put into rivers or into the sea, and there are few laws to 49 this. We also know that if the 50 of the world continues to rise at the present rate, in a few years, there won't be enough food. What can we do to solve the 51 ? If we eat more vegetables and less 52 , there will be more food available for everyone. Land that is used to grow crops feeds five times more people than land where animals are kept. Our natural resources will 53 longer if we learn to recycle them. The world population will not 54 so quickly if people use modern methods of birth control. Finally, if we 55 people to think about the problems we shall have a better and cleaner planet in the future.
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