The Belsen interview is a means of pretesting media surveys. It gathers facts and figures by asking people about their attitudes, beliefs and awareness of various media. With this technique, the respondent is interviewed twice-first by an interviewer using the proposed survey and then by a different interviewer, who asks questions about the survey itself. The Belsen interview uses __________ data.
a) Observational
b) Secondary
c) Intercept
d) Questionnaire
e) Synergistic