Which of the following presents the greatest challenge to modern opinion research?

Which of the following presents the greatest challenge to modern opinion research?
 
  a. Population mobility
   b. Increased diversity
  c. Availability of the Internet
   d. A shift in telephone ownership and usage

Question -2-

By the mid-1980s, what was the main way of gathering opinions?
 
  a. Straw polling
  b. In-person polling
  c. Telephone polling
   d. Mail polling

Question -3-

What is the name given to the technique used during political campaigns in an attempt to persuade voters to vote for (or against) a particular candidate, or not bother going to the polls at all?
 
  a. Call-in polls
   b. Push polls
  c. Unscientific polls
   d. Single-question polls

Question -4-

Which of the following is not an example of an unscientific poll?
 
  a. A call-in poll
  b. A straw poll
  c. A Gallup poll
   d. A single-question poll on a website