Why would it be important to have a true representative sample when talking about public opinion ?

1.     in what kind of government does a small group have a firm control over a country?  

During the industrial revolution, many governmentsadopted an economic system called capitalism. in thissystem, governments allowed businesses to operate asfreely as possible, capitalism led to economic growth inmany countries and a small number of peoplebecome very wealthy. however the system could be harshfor poor workers, who often worked long hours in unsafeconditions just to make enough money to eat. as a result,some workers turned against capitalism and demandedthat their governments take more control over theireconomies.which statement best describes the passages main idea? a. capitalism was beneficial for some people during the industrialrevolution, but others opposed the system.b. capitalism was mostly a cause of problems during the industrialrevolution, which led to its eventual collapse.c. capitalism became the favored economic system for manycountries during the industrial revolution.d. capitalism was to countries during the industrialrevolution, but became a problem after the revolution ended.edit: correct answer is a

Me with these dbq articles 1. whether its reliable? why or why not? 2. what's the main idea 3. demonstrating new deal as success or failure?