The correct answer is option 'C' - Once.

Explanation:
The Lok Sabha is the lower house of the Parliament of India and its term is generally for a period of five years. However, there are certain circumstances where the term of the Lok Sabha can be extended beyond five years. Let's examine the instances when the term of the Lok Sabha was extended:

1. National Emergency:
- Under Article 352 of the Indian Constitution, the President of India can declare a state of emergency if he/she is satisfied that the security of India or any part thereof is threatened by war or external aggression or armed rebellion.
- During a National Emergency, the term of the Lok Sabha can be extended for a period not exceeding one year at a time.
- However, the extension can only be granted if such an extension is approved by a resolution passed by both Houses of Parliament.

2. Proclamation of Emergency due to Internal Disturbance:
- Under Article 356 of the Indian Constitution, the President can declare a state of Emergency if he/she is satisfied that the governance of a state cannot be carried out in accordance with the provisions of the Constitution.
- In such cases, if the Lok Sabha has been dissolved, the term of the Lok Sabha can be extended for a period not exceeding one year at a time.
- Similar to the National Emergency, the extension can only be granted if approved by a resolution passed by both Houses of Parliament.

Based on the above points, it can be concluded that the term of the Lok Sabha has been extended only once in India's history. This happened during the National Emergency declared in 1975 by then Prime Minister Indira Gandhi. The Lok Sabha's term was extended for a period exceeding five years, but less than six years, until the emergency was lifted in 1977.

Therefore, the correct answer is option 'C' - Once.