If you have a lot of potential referral sources, follow-up questions can be a great way to add additional response options. For example, if the question is "How did you hear about us?" and one of your response options is "Social Media" you can add follow up options like "Facebook", "Instagram", or "SnapChat".
Here's an example of setting up a survey with response options:
In the above example, if one of your customers chooses the option "I search online for sunglasses" they will then be displayed options for Google, Bing, Yahoo, and other.