What is the maiidea of the passage
·The theory of relativity.
·Exactness is the core of science.
·Scientists are different from ordinary people.
·Exactness and ways of using tools are the keys to the making of a scientist.

单选题
·The way he uses his tools.
·the difference between scientists and ordinary people
·works not only under one set of conditions at one time, but also under the same conditions at other times
·that the investigations are important in science
·Exactness and ways of using tools are the keys to the making of a scientist.