阅读理解。阅读下列短文, 从给的四个选项 (A、B、C和D) 中, 选出最佳选项。
What makes a person a scientist？Does he have ways or tools of learning that are different from those of others？The answer is “NO”．It is not what the tools that a scientist uses but how he uses these tools that makes him a scientist.You will probably agree that knowing how to use the power is important to a carpenter (木匠)．You will probably agree，too，that knowing how to investigate (调查)，how to discover information，is important to everyone.The scientist，however，goes one step further，he must be sure that he has a reasonable answer to his questions and that his answer can be confirmed (确认) by other persons.He also works to fit the answers he gets to many questions into a large set of ideas about how the world works.
The scientist’s knowledge must be exact.There is no room for half right or right just half the time.He must be as nearly right as the conditions permit.What works under one set of conditions sometimes must work under the same conditions at other times.If the conditions are different，any changes the scientist observes in a demonstration (演示) must be explained by the changes in the conditions.This is one reason that investigations are important in science.Albert Einstein，who developed the theory of relativity，arrived at this theory through mathematics.The accuracy of his mathematics was later tested through investigations.Einstein’s ideas were shown to be correct.A scientist uses many tools for measurements.Then the measurements are used to make mathematical calculations that may test his investigations.
