The correct answer is January.
Bihar is a state in India that is located in the eastern part of the country. The state has a humid subtropical climate, with hot summers and mild winters. The coldest month of the year in Bihar is January, when the average temperature ranges from 10°C to 20°C.
The other options are incorrect because they are not the coldest months of the year in Bihar. December is the second coldest month, with an average temperature of 12°C. February is the third coldest month, with an average temperature of 14°C. November is the fourth coldest month, with an average temperature of 16°C.
The coldest months of the year in Bihar are January and December. The average temperature in January is 10°C, while the average temperature in December is 12°C. The coldest months are also the driest months of the year, with very little rainfall.