The correct answer is c) Summer (monsoon).
The monsoon is a seasonal wind pattern that brings heavy rains to South Asia. It is caused by the difference in temperature between the land and the ocean. In the summer, the land heats up faster than the ocean, causing the air to rise. This creates an area of low pressure over the land. The air from the ocean, which is cooler and has higher pressure, flows in to fill this low pressure area. This flow of air is what causes the monsoon rains.
Bihar is located in the eastern part of India, which is one of the areas that receives the most rainfall from the monsoon. The monsoon rains are essential for agriculture in Bihar, as they provide the water that is needed to grow crops. The monsoon also helps to replenish the groundwater supplies in Bihar.
The other options are incorrect because they are not the seasons that bring the majority of rainfall to Bihar. Winter is the dry season in Bihar, while spring and autumn are the transitional seasons between winter and summer.