Explanation:

- Option 1: Tenth year

- The Indian Census is conducted every ten years.

- It is a comprehensive exercise to collect demographic data across the country.

- This is the correct option.

- Option 2: Fourth year

- Conducting every four years is not the practice for the Indian Census.

- Other surveys or studies might be conducted at different intervals.

- Option 3: Fifth year

- A five-year gap is not enough for such a large-scale survey in India.

- Other national or economic surveys could occur on a five-year basis.

- Option 4: Seventh year

- A seven-year cycle is not applicable to the Indian Census.

- Demands significant planning over the decade for accuracy.