You can configure requirements in a form for allowing users to submit a a response, or add a CAPTCHA to prevent automated responses.
Setting the conditions under which the user can submit a response
The submit button can be shown or hidden depending on how the user responded to the questions. For example, you can allow submits only by users from a specific city.
Select a form and go to Settings → Text and submit logic.
Under Form submission button, select Activate button → On condition.
Set the condition under which the user can submit a response:
Select the question that determines whether to show or hide the submit button.
The submit button will be disabled if the selected question is hidden in the form based on a condition.
Select the comparison operator: equal or not equal.
Select or enter the answer that the user's input has to match.
If you need to allow submitting a response only when multiple conditions are met, click under the first condition. Set up the condition: select a question, a comparison operation, and an answer option.
The new condition will be grouped with the existing ones. By default, all conditions within the group are combined using the AND operator, so the user can submit their response only if all conditions are met simultaneously. If you want users to be able to submit responses when at least one condition is met, click the operator icon to the left of the group to select the logical OR instead.
To set a more complex logic, add multiple groups of conditions. To do this, click Add condition under the list of conditions, then configure the conditions within the group and select a logical operator to apply to them: AND or OR.
To delete a condition, hover over it and click to the right.