Translations:Surveys - introduction/92/en
From LimeSurvey Manual
If it has been already chosen from the global settings by the superadministrator to have the "no answer" option displayed, then the Show "No answer" of the local survey field becomes non-selectable because the global settings trump the survey settings (idem for the Off case). To offer freedom to your survey administrators, the superadministrator has to choose Selectable for the Show "No answer" option from the global settings of your LimeSurvey installation.