After pulpotomy of a permanent central incisor in an 8-year old child, the most important clinical criterion/criteria of success is/are:
1. completion of root formation.
2. retained natural colour of the tooth.
3. secondary dentin bridge formation.
4. formation of pulp stones.

(1) and (3)

(1) (2) (3)

(2) and (4)

(4) only

All of the above.