The questions in the questionnaire, are built from attributes that are contained in placeholders and conditions.
In order for the question to be deleted, all instances of the attribute must be removed from the source.
Go into live demo and show condition logic and control f to find what you’re looking for and you can delete it.
As illustrated in the screenshot below, if you wanted to find 'limb 2', click on live demo and then show condition logic. You would then click Control f and search for 'limb 2'.