Apolitical party sends a mail survey to 1500 randomly selected registered voters in a community. the survey asks respondents to give an opinion about the job performance of the current president. of the 1500 surveys sent out, 480 are returned, and of these, only 120 say they're satisfied with the president's job performance. this is an example of a survey with:

a. little bias because an individual will know for certain whether they approve of the president's job performance.
b. little bias because 1500 voters represent an important part of his district.
c. no bias.
d. none of the answer choices is correct.