Written responses are especially useful if you want to collect certain feedback in written form.

These written responses could be used if there are too many answer options for a multiple choice question or you would like some keywords to a certain topic.
You shouldn't expect your testers to write a long paragraph rather than a few words or one/two sentences.

Just write your desired question in the textbox:

 

This is what the question would look like for a tester during this task: