Letting respondents decide if they want to answer a specific question or not will lead to higher submission/ completion rates. 

However, in some cases questions may need to be mandatory to answer. For example, if you want to follow-up on specific customer feedback by phone and need to collect someone's phone number.

Select the 'Edit question settings' icon on the right-hand side for a specific question.  

The following window opens:

Select the checkbox and then 'Ok' button. An asterisk (*) will appear behind the specific question to indicate that this question is now required. 

Respondents will also see the asterisk with the question on the form. If one tries to skip the question, an error message appears.

The default error message is 'Deze vraag is verplicht'.
Change the required question error message under Form settings > Error messages.

By default, the rating question use a 5 point scale where 1 is 'Very dissatisfied' and 5 'Very satisfied'. Under the question settings, these can both be changed. 

Select the  'Edit question settings' button. The following window will open:

Via the drop-down choose a scale between 3 and 10 points: