(3 points) A Senator wants to know what the voters of his state think of proposed legislation on gun control. He mails a questionnaire on the subject to an SRS of 2500 voters in his state. His staff reports that 448 questionnaires have been returned, 343 of which support the legislation. (a) The population is A. the voters in his state. B. the 2500 voters receiving the questionnaire. C. the 448 letters received. D. the 343 letters supporting the legislation. (b) The sample is A. the 2500 voters receiving the questionnaire B. the 448 letters received. C. the 343 letters supporting the legislation. D. the voters in his state. (c) This is an example of A. a survey with little bias because a large SRS was used. B. a survey containing nonresponse. C. a survey with little bias because it was the voters who elected the senator. D. all of the above.