The correct answer for this question is option 3: 12.00 noon. In the Indian Parliament, Zero Hour refers to the time allocated for Members of Parliament to raise important matters without any prior notice. It is an essential part of parliamentary proceedings and allows MPs to bring urgent matters to the attention of the government.

Zero Hour generally starts at 12.00 noon, as specified in the parliamentary schedule. During this time, MPs can make brief speeches or ask questions on issues that are of public importance but do not have a fixed time slot in the parliamentary agenda.

Option 1, stating that Zero Hour starts in the first hour of the sitting, is incorrect. Option 2, claiming that it starts in the last hour of the sitting, is also incorrect. Both of these options do not align with the established time of 12.00 noon.

Option 4, suggesting that Zero Hour has no fixed timings, is not accurate. While the specific duration of Zero Hour may vary, it does have a fixed starting time at 12.00 noon.

Therefore, the correct answer is option 3: 12.00 noon.