The correct answer is D) scientific-polling groups.
The Gallup Organization and the Pew Research Center for the People and the Press are the best-known examples of scientific-polling groups.
These scientific-polling groups have the special job of describing the public opinion of Americans in determined situations. The Gallup Organization and the Pew Research Center for the People and the Press randomly select the people who are about to be polled. This creates the right scenario to validate the results in an objective and accurate manner, without tendencies. This is very important in polls, the veracity of the information and the numbers.