According to Census 2011, the State having the highest density of population is

Bihar
Kerala
Uttar Pradesh
West Bengal

The correct answer is (b), Kerala.

Kerala has the highest population density in India, with 860 people per square kilometer. This is more than double the national average of 382 people per square kilometer. The state’s high population density is due to a number of factors, including its small size, fertile land, and warm climate.

Bihar, Uttar Pradesh, and West Bengal are also densely populated states, but they have lower population densities than Kerala. Bihar has a population density of 1,106 people per square kilometer, Uttar Pradesh has a population density of 828 people per square kilometer, and West Bengal has a population density of 880 people per square kilometer.

The high population density in Kerala has a number of implications for the state. It puts a strain on resources such as land, water, and energy. It also contributes to pollution and environmental degradation. The state government has taken a number of measures to address the challenges of high population density, including promoting family planning and investing in infrastructure.

Bihar, Uttar Pradesh, and West Bengal also face challenges related to their high population densities. These states have large populations of poor and marginalized people. They also have high rates of illiteracy and unemployment. The state governments in these states are working to improve the lives of their people, but they face a number of challenges.