The reason for India being a major producer of different varieties of fruits and vegetables is primarily due to the variation in its agro-climatic conditions. Agro-climatic conditions refer to the climate, soil type, and topography of a particular region, which play a crucial role in determining the suitability of cultivating certain crops.

India has a diverse range of agro-climatic conditions, ranging from tropical and sub-tropical regions to temperate and alpine regions. This diversity allows for the cultivation of a wide variety of fruits and vegetables throughout the country. For example, tropical regions like Kerala and Maharashtra are known for producing tropical fruits like mangoes and bananas, while colder regions like Himachal Pradesh are known for their apple orchards.

While options 1 and 2 (large population size and large land area) may indirectly contribute to India`s agricultural productivity, they are not the primary reason for the country`s success in producing different varieties of fruits and vegetables. Similarly, option 4 (diversity in socio-cultural phenomenon) is unrelated to the agricultural factors affecting fruit and vegetable production.

In conclusion, option 3 is the correct answer as the variation in agro-climatic conditions in India plays a crucial role in making it a major producer of different