Do you suppose Darwin, one of the greatest scientists of all times, really
did fools' experiments?  
Or did he do experiments that were so simple and basic that other people just thought they were foolish?
Sometimes people think they already know the answer to a question or the solution (解决办法) to a problem. Sometimes they really do know an answer or a solution, but without thinking they are important.
Charles Darwin didn’t settle for (满足于) just thinking he knew something. And, he believed all things could be important however simple they seemed to be.
Suppose you drop two sheets of paper which are exactly the same size and shape. If you drop them at the same time in the same place, they will fall in the same way. Now make one of the sheets of paper into a tight little ball and let it drop along with the other sheet. What happens? You have done an experiment that is so simple that you might think it couldn't be worth anything.
But this simple experiment is important. It explains part of our present-day understanding of physics ideas that were worked out long ago by Galileo and Newton. And these understandings set aside some of ancient Greek physics.
Science sometimes stops to look at very simple things and to think very hard about them. Even the simplest idea, what we might think is foolish, can shake the foundations (基础) of science.
68. “Sometimes people think they already know the answer to a question.” This means that _________.
A. they are already told the answer
B. the question is so important that everyone should know the answer
C. they are already to answer such a question by others
D. the question is simple enough for them to answer
69. From the passage, we learn that Charles Darwin _________.
A. did many fools' experiments
B. enjoyed doing simple experiments
C. was not satisfied with what he knew
D. tried to prove that Galileo and Newton were sometimes wrong
70. The underlined phrase “set aside” most probably means “________”
A. throw away        B. store up     B. put to use       D. realize
71. The author of the passage tries to ________.
A. convince(使…信服) us that Charles Darwin, Galileo and  Newton are the greatest scientists in the world
B. draw the conclusion that basic sciences are simple things
C. prove that two sheets of paper, with the same size and shape, will fall at the same speed
D. draw our attention to everyday happenings around us