By clicking on visibility settings, we can collect between two types of integration of questions into the survey:
<UL>
<LI> <b> visible </b> question to be visible to respondents in the final questionnaire
<LI> <b> hidden </b> question that will only be visible to the author when editing the questionnaire. We use the option either for a hidden address or for the system variable e-mail, which respondents do not need to fill in.
