A preparation for a porcelain fused to metal crown with a porcelain butt joint margin should have a
1. 90o cavosurface margin.
2. subgingival finish line.
3. 1.2mm shoulder.
4. 90o axiogingival angle.

(2) and (4)

(1) and (3)

(1) (2) (3)

All of the above.

(4) only