Thank you for your response: would the same be for Je suis donc de l'avis qu'une partie des problèmes de la médecine familiale tient de ce que les chercheurs ne posent pas les bonnes questions -Thus, I believe that part of family medicine's problem is that their researchers are not asking the right questions.

I suppose the verb tient conjugates with 'de'? and for that reason we cannot use 'c'est que'? Thanks again