Which of the following should be done prior to pin hole placement in an extensive amalgam preparation?
1. Examine the radiograph.
2. Determine the subgingival anatomic contours.
3. Remove caries and unsupported enamel.
4. Place a pilot hole at the dentino-enamel junction.

All of the above.

(4) only

(2) and (4)

(1) and (3)

(1) (2) (3)