Explanation:
The correct answer is option 'B' - Rabi.

Understanding the seasons:
In India, there are three main seasons - summer, rainy, and winter. Each season has its own characteristics and is associated with different agricultural practices.

Summer season:
The summer season is the hottest season of the year and typically lasts from March to May. During this season, the temperature is high, and there is limited rainfall. Farmers usually grow crops like watermelon, cucumber, and mangoes during this time.

Rainy season:
The rainy season, also known as the monsoon season, occurs from June to September. This is when the country receives most of its annual rainfall. The rainwater is important for agricultural activities as it helps in growing crops. Farmers typically grow crops like rice, maize, and soybeans during this season.

Autumn season:
Autumn is the season that follows the rainy season. It marks the transition between summer and winter and is characterized by cooler temperatures and less rainfall. The autumn season typically starts in September and lasts until November. During this time, the weather becomes more favorable for certain crops.

The start of Rabi season:
The Rabi season starts when the rainy season ends and autumn begins. It is the second main agricultural season in India and lasts from October to March. During this season, the weather is relatively cooler, and there is less rainfall. This makes it suitable for the cultivation of various crops.

Crops grown during Rabi season:
Some of the major crops grown during the Rabi season include wheat, barley, mustard, peas, and gram. These crops require a cool and dry climate, which is why they are cultivated during the winter months.

Conclusion:
In conclusion, the Rabi season starts when the rainy season ends and autumn begins. This season is characterized by cooler temperatures and less rainfall, making it suitable for the cultivation of crops like wheat, barley, and mustard.