What makes a person ascientist? Does he have ways or tools of learning that are different from thoseof others? The answer is "no".It is not the tools a scientist usesbut how
he uses these tools that make him a scientist.You will probably agree thatknowing how to use a power is important to a carpenter.You will probably agree,too, that
knowing how to investigate, how to discover information, is important toeveryone.The scientist, however, goes one step further, he must be sure that hehas a reasonable
answer to his questions and that his answer can be confirmed by other persons.Healso works to fit the answers he gets to many questions into a large set ofideas about how
the world works.
The scientist's knowledge must be exact.There is no room for half right orright just half the time.He must be as nearly right as the conditions permit.Whatworks under one
set of conditions at one time must work under the same conditions at othertimes.If the conditions are different, any changes the scientist observes in ademonstration must be
explained by the changes in the conditions.This is one reason thatinvestigations are important in science.Albert Einstein, who developed thetheory of relativity, arrived at
this theory through mathematics.The accuracy of his mathematics was latertested through investigations, and Einstein's ideas were shown to be correct Ascientist uses many
tools for measurements.Then the measurements are used to make mathematicalcalculations that may test his investigations.

A sound scientifictheory should be one that ___________.

A.works not only under one set of conditions at one time, but also under thesame conditions at other times

B.does not allow any changes even under different conditions

C.can be used for many purposes

D.leave no room for improvement