Do you suppose Darwin, one of the greatest scientists of all time, really did foolish 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 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 sheets of paper that are of 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 sheets. 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 understandings of physics, ideas that were worked out long ago by Galileo and Newton. And these understandings set aside some of ancient Greek physics.

           Scientists sometimes stop to look at very simple things and to think very hard about them. Even the simplest idea, which we might think is foolish, can shake the foundations of science.

若用北师版初中数学教材上使用的计算器，依照下列按键的顺序，显示的结果应为（   ）