Correct Answer: (b) West Bengal and Arunachal Pradesh
Solution:According to the Census 2001, West Bengal had the highest population density, which was 903 and Arunachal Pradesh had the lowest population density (13). As per Census 2011, India's most densely populated State is Bihar (1106 persons per sq. km) and the State with the lowest population density is Arunachal Pradesh (17 persons per sq. km).