Answer:
Every 20th student who walks by the student center is the correct answer.
Explanation:
Option B is not correct, unless the newspaper contains relevant information about the movies; however, it is possible to get this information from other sources.
C is also incorrect because the freshman at a particular school are juts a percentage of the total population and a limited group.
Letter D is also incorrect because people in a computer class don't necessarily read the paper.
However, option A is the correct answer since it is a controlled environment and it can easily be analyzed.
