to find the best singer, having viewers call ...

# Brief Explanations: When viewers call or text their vote for a TV - show poll to find the best singer, not all viewers are equally likely to respond. Some may not have access to call or text, or may not be interested in participating. This leads to a situation where the sample of respondents is not representative of the entire population of viewers, which is non - response bias. Over - coverage means including elements that should not be in the population, under - coverage means excluding elements that should be in the population, and interviewer bias involves the influence of the interviewer on the responses. Here, the main issue is non - response bias. # Answer: B. nonresponse bias