The areas where the monthly rainfall during October to December ranges between 10 cm and 30 cm mainly lie in which parts of India?

Introduction / Context:
Seasonal distribution of rainfall across India is a fundamental concept in Indian climatology. While much of the country receives the bulk of its rainfall during the south west monsoon (June to September), some regions receive significant rainfall during the retreating or north east monsoon season, particularly from October to December. This question asks you to identify which parts of India typically receive between 10 cm and 30 cm of rain per month during this October to December period, highlighting the special role of the retreating monsoon along the south eastern coast.

Given Data / Assumptions:

The time period considered is October to December, which corresponds mainly to the retreating monsoon season.
The monthly rainfall range is given as 10 cm to 30 cm, indicating moderate to heavy rainfall for that season.
The options list different regions: south eastern coastal states, south western coastal states, and Himalayan states in the north.
We assume normal climatic conditions without extreme anomalies like cyclones beyond the usual pattern.

Concept / Approach:
The key concept is the distinction between the south west monsoon and the north east or retreating monsoon. Most of India, including the Western Ghats and northern states, gets its main rainfall from the south west monsoon. However, the Coromandel Coast, particularly eastern Tamil Nadu and parts of coastal Andhra Pradesh, gets comparatively less rain from the south west monsoon and instead receives a large portion of its annual rainfall from the north east monsoon and associated cyclonic disturbances in the Bay of Bengal during October to December. Therefore, when a question mentions appreciable rainfall in this period, you should think of the south eastern coast rather than the western or northern hill regions.

Step-by-Step Solution:

Verification / Alternative check:
You can verify this by referring to isohyet maps or monthly rainfall charts from geography textbooks. These maps usually show high rainfall zones along the Coromandel Coast in October and November, indicating the impact of the retreating monsoon and associated cyclones. Additionally, news reports about cyclones making landfall near Chennai, Cuddalore, or Nellore during this period are common, which supports the idea that this coast experiences heavy late season rainfall. In contrast, Kerala and Karnataka are more famous for heavy rainfall during June to September, and the Himalayan states have a different pattern with winter snowfall and rain from western disturbances.

Why Other Options Are Wrong:

Common Pitfalls:
A frequent mistake is to assume that coastal regions like Kerala always receive heavy rainfall throughout the year because they are on the windward side of the Western Ghats. Another pitfall is to ignore the seasonal shift in wind direction and cyclone tracks that make the south eastern coast unique in the retreating monsoon period. To avoid such confusion, always link the time period mentioned in the question with the known rainfall regime of each region. Remember that the Coromandel Coast is the key beneficiary of the north east monsoon and cyclonic storms between October and December.

Final Answer:
The correct answer is Eastern parts of Tamil Nadu and coastal Andhra Pradesh, because this region receives significant rainfall from the retreating monsoon and cyclonic storms between October and December, often in the range of 10 cm to 30 cm per month.