Explanation:

- Kanyadan: This is a ritual where the bride's parents give away their daughter to the groom. It is significant but not obligatory under the Hindu Marriage Act.

- Panigrahan: This involves the groom holding the bride’s hand, symbolizing mutual acceptance. Like Kanyadan, it is a respected ritual but not mandatory under the law.

- Saptapadi: This is the ritual where the couple takes seven steps around a sacred fire, making vows to each other. It is essential for a Hindu marriage to be considered complete and legally valid under the Hindu Marriage Act.

- All of the above: This would suggest all the listed ceremonies are obligatory, which is not the case.

- Correct Answer: Option 3 - Saptapadi