The correct answer is option D, which states that the Nabam Rebia case is related to disqualification petitions under the anti-defection law. Let's understand the context and details of this case.

Context:
The Nabam Rebia case refers to a legal dispute that arose within the Arunachal Pradesh Legislative Assembly in 2015. This case gained significant attention and was widely covered in the news due to its political implications and its impact on the anti-defection law.

Background:
In December 2015, there was a political crisis in Arunachal Pradesh, where the ruling Congress party faced a rebellion from a faction of its own Members of Legislative Assembly (MLAs). The Governor of Arunachal Pradesh, Jyoti Prasad Rajkhowa, advanced the assembly session without consulting the Chief Minister, Nabam Tuki, and the Speaker, Nabam Rebia.

The Speaker subsequently disqualified 14 rebel MLAs under the anti-defection law for their alleged anti-party activities. These disqualified MLAs, along with opposition parties, challenged the Speaker's decision in the Guwahati High Court.

Key Points:
1. Anti-Defection Law: The anti-defection law, also known as the Tenth Schedule of the Indian Constitution, was introduced in 1985 to combat political defections and maintain the stability of the government. It specifies the grounds on which an elected representative can be disqualified from their position.

2. Disqualification Petitions: Disqualification petitions can be filed under the anti-defection law when a member of a legislative body is alleged to have violated the provisions of the law. These petitions are usually filed with the Speaker of the concerned legislative assembly or the Chairman of the Rajya Sabha or the Lok Sabha.

3. Role of the Speaker: The Speaker plays a crucial role in deciding the disqualification petitions under the anti-defection law. They examine the evidence, listen to arguments from both sides, and make a decision based on the provisions of the law.

4. Guwahati High Court Judgment: The Guwahati High Court, in its judgment on the Nabam Rebia case, held that the Governor's decision to advance the assembly session was unconstitutional. It also quashed the Speaker's decision to disqualify the rebel MLAs, stating that the disqualification process was not conducted in accordance with the principles of natural justice.

5. Supreme Court's Verdict: The matter eventually reached the Supreme Court, which upheld the High Court's judgment and ruled that the Governor's actions were unconstitutional. The Supreme Court reinstated Nabam Tuki as the Chief Minister and Nabam Rebia as the Speaker.

Conclusion:
The Nabam Rebia case is significant as it highlighted the role of the Speaker in deciding disqualification petitions under the anti-defection law. It also emphasized the importance of upholding the principles of natural justice in such cases. This case serves as a precedent for future interpretations and applications of the anti-defection law.