Which&nbspbest&nbspdescribes bias, if any, from the sample surveye

Which best describes bias, if any, from the sample surveyed? survey: voter preference in an upcoming election sample: randomly selected people at a large rally for one of the candidates A.Since the sample is randomly selected, there is unlikely to be any bias. B.Since the rally is for one of the candidates, there is likely to be bias in favor of that candidate. C.Since the rally is for one of the candidates, there is likely to be bias against that candidate. D.Since the rally is large, the sample will be large enough that bias is unlikely.