You can label a specific question as mandatory in the 'EDIT' – 'Questionnaire' tab, in the right-hand side menu, which is accessed by clicking on the question you want to edit. You can choose from the following options in the 'Mandatory question' category:
1. No reminder, by which the respondent is not required to answer the question;
2. Soft reminder: the application will warn the respondent of the unanswered question, but will nonetheless allow them to continue;
3. Hard reminder: the application will not allow the respondent to continue until the question has been answered.