Some question types are mandatory by default, so it's not possible for respondents to skip them.
The following questions are required:
Single answer selection
Multiple answer selection
NPS (Net Promoter Score)
Smiley Scale
Survey Invitation
Rating question
Matrix question
The following question types have the requirement selectable (can be made non-mandatory):
Text Answer question
Contact form question
Date question
Dropdown list question
Text answer, Date and Dropdown questions
To make text, date, or dropdown questions mandatory, go to the settings of the question and enable the answer required option:
Contact form question
To make a contact form question required, click on the ⭐ star icon next to the field you'd like to make required:
💡 When a Consent checkbox is added to a Contact form question, it becomes mandatory.