Explanation:

- Antiquity: A custom must have been practiced for a long period to be considered valid. It needs historical precedent.

- Certainty: A valid custom must be clearly defined and consistently recognizable. It's not subject to individual interpretation.

- Consistency: The practice should occur uniformly over time, without any major deviations or interruptions.

- All of the above: A valid custom typically requires all these elements to ensure it is established, clear, and followed consistently.

Your answer:

Option 4: All of the above