Since I don't know the context of this question, I'll answer it the way a scientist would.
We know that Einstein was a scientist. Scientists are always asking questions and creating tests to solve problems. Einstein most likely didn't view his achievements as the answer to the problems of the universe. He probably saw a lot of flaws in his work. Even if he didn't, a true scientist is always questioning things. The definition of a scientific law is a theory that has never been proven false. He probably wanted to know if his achievements were theories or if they were laws.
These are just a few ideas. Take a minute to think about the context of the question and what you think that the answer should be based on that.
The correct answers:
1) tainted source is adulterated, biased and corrupted information that may eventually affect a study, trial, investigation.
2. Historical research is important because it can help students and teachers (masters, professors, educators) understanding with assurance the fact in a essay/ study/ investigation. The main purpose of historical research is preserving and interpreting facts correctly.
example of dubious secondary information: fake news, when there is divergent information about an official source of information. Often the source language is not appropriate, accurate, and unbiased.
The answers are
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More railroads lead to lesser land for crop cultivation and raising of livestock! hence, farmers are unable to earn profit from their activities.