The concept of single citizenship in the Indian Constitution is inspired by England. Single citizenship means that all Indian citizens are governed by a unified set of laws and have the same fundamental rights and duties, regardless of the state they belong to. This concept is derived from England, where there is only one citizenship for all the citizens of the country, without any distinction made based on different states or regions. Germany, France, and Ireland, on the other hand, have a concept of dual citizenship, where citizens have rights and obligations both at the national level and at the level of their respective states or regions. Therefore, the correct answer is option 4.