Sample A
I do not think that this would provide a true representation of the public's opinion.  First of all, Not everyone in the community necessarily listens to that particular station or show.  And not all of them would call in.  So summarizing, the number of people who do call in probably falls short of the majority of the poputlation.  That very vaguely represents the public's voice on whatever matter is a hand.

Sample B
Me and my friends listen to the radio and call in all the time.  I think this survey is true.

Sample C
The results of this radio station's daily polls will only represent the opinions of those who listen to the program and choose to participate in the survey.  Listeners who do not participate in the survey are likely to be under represented and people who do not listen to that particular station or show will not be represented at all.  The public has a wide variety of tastes and it is unlikely that a call in survey of one particular station or format would provide a true representation of the public's opinion.

Teacher Comments
This exit slip was used near the end of a unit on statistics after several class discussions on representative data and misleading statistics.   I was looking for students to provide a negative answer to this question and then support their choice by mentioning that not even a representative proportion of the population concerned with the issue is likely to be listening to the station at that time and respond to the survey.  Because all students gave a response related to the question within the time allowed, all received 10 of 10 points.  Although response A was not as clearly presented as response C, both were awarded 12 points (2 bonus points) for the assignment since they showed evidence of understandig the concept I was evaluating.

Student volunteers were asked to share their reponses the following class period.   The discussion that followed helped those students with responses similar to response B to understand that public in this question refers to all groups in the population and not just those within their peer group.