The passage states that the 1949 Constitution of India, with 395 articles, is the wordiest of all national constitutions.
This clearly identifies India as having the longest constitution among nations.
Option (a) Great Britain — does not have a single codified constitution; its constitutional laws are spread across statutes, conventions, and customs.
Option (c) Puerto Rico — mentioned as having a concise constitution (9,000–15,000 words), making it among the shortest, not the longest.
Option (d) Soviet Union — while the passage discusses the 1936 Soviet constitution, it does not claim it to be the longest, and it is certainly shorter than India’s.
Therefore, India is the correct answer.