1、Everyone knows that _____ is dangerous to play with fire,but _____ is diffrcult is to prevent children from playing with me.A、it\it     B、what\what     C、it\what     D、what\it2、But for the help you gave me,I _____ the exam nations.A、would have passed     B、would pass     C、wouldn't have passed     D、wouldn't pass3、They told me it would be cheap but _____ it cost me nearly