The canal of a maxillary canine has been instrumented to within 1mm of the apex and is ready to be obturated. A radiograph indicates that the master cone is 2.5mm short of the apex. The most appropriate management is to ________.
1) proceed with the filling as the cone is within acceptable limits.
2) fit a larger cone within 2mm of the apex.
3) cut the cone 1mm and insert.
4) discard the cone and fit a smaller one.