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

单项选择题
完形填空
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.
小题1:
A.resourcesB.sourcesC.materialsD.matter
小题2:
A.commonB.the sameC.changeableD.different
小题3:
A.crowdedB.pollutedC.dirtyD.busy
小题4:
A.producingB.using upC.reducingD.making
小题5:
A.protectingB.savingC.pollutingD.fighting
小题6:
A.tryB.continueC.stopD.have
小题7:
A.liveB.lastC.continueD.survive
小题8:
A.fishB.seagullsC.crocodilesD.frogs
小题9:
A.polesB.boatsC.methodsD.ideas
小题10:
A.mountainsB.the seaC.cropsD.forests
小题11:
A.growB.plantC.saveD.cut down
小题12:
A.plantB.cut downC.saveD.burn down
小题13:
A.ThusB.HoweverC.Generally speakingD.Therefore
小题14:
A.encourageB.neglectC.stopD.wake up
小题15:
A.productionB.pollutionC.populationD.revolution
小题16:
A.pollutionB.environmentC.questionsD.problems
小题17:
A.fruitB.meatC.fishD.grain
小题18:
A.useB.stayC.keepD.last
小题19:
A.raiseB.riseC.runD.grow
小题20:
A.forceB.helpC.educateD.show