Please list all the common questions in 2014's survey and 2016's survey.
question refers to questiontext; all the common questions in 2014's survey and 2016's survey refers to QuestionID(SurveyID(2014)) = QuestionID(SurveyID(2016))

SELECT T1.questiontext FROM Question AS T1 INNER JOIN Answer AS T2 ON T1.questionid = T2.QuestionID WHERE T2.SurveyID IN (2014, 2016) GROUP BY T1.questiontext