In the Vedic Age trade was limited because of isolationism, causing people not to trade with each other
poor roads, causing people to use the river ways to engage in trade
poor trading products, causing people not to desire the goods others made
widespread war, causing trade to stop between groups in conflict

it was douglas macarthur..

the correct answer is:   the domino theory states that if one country in a region came under the influence of communism, then the surrounding countries would follow in a domino effect.

i believe it would influence their own way of understanding things. it shall be a foundation where they can draw or start an argument.   historians are also  scientists that  have their tools of analysis and expertise to unlock a variety of difficulties such as relationships of man, origin, politics, economy, and culture. based on facts and understanding on these areas, they may shade light to extract ideas and develop options to validate a hypothesis or debunk it.