The preparation of an anterior tooth for a porcelain fused to metal crown should provide
1. adequate length for retention-resistance.
2. space for a thickness of metal that will resist deformation.
3. space for a thickness of porcelain that will be esthetic.
4. a single path of insertion.

(4) only

(2) and (4)

(1) and (3)

(1) (2) (3)

All of the above.