The correct answer is: b) June to September.
The state receives the highest rainfall during the months of June to September because of the southwest monsoon. The southwest monsoon is a seasonal wind that blows from the southwest towards the northeast during the summer months. It brings heavy rainfall to the Indian subcontinent, including the state in question.
The other options are incorrect because they do not correspond to the months when the state receives the highest rainfall. Option a) December and January is the winter season in India, and there is usually very little rainfall during this time of year. Option c) March to May is the spring season, and there is some rainfall during this time of year, but it is not as heavy as the rainfall during the monsoon season. Option d) October and November is the autumn season, and there is also some rainfall during this time of year, but it is not as heavy as the rainfall during the monsoon season.