Which of the Following Is True About Mass Opinion Surveys

Which of the following is true about mass opinion surveys?

A) They have become more accurate over time because of the increase in Internet polls.
B) They have become so sophisticated that scientists have been able to eliminate any margin of error.
C) They are a powerful tool for measuring public opinion but should be interpreted carefully.
D) They should never be trusted because samples are almost always biased.
E) They cannot give an accurate picture of public opinion.