Correct Answer:
D. 7 years
The Constitution of Pakistan 1962 remained in effect for approximately 7 years. Promulgated by President Ayub Khan on June 8, 1962, it introduced a presidential system of government. This constitution was eventually abrogated on March 25, 1969, when General Yahya Khan imposed martial law, effectively ending Ayub Khan's rule and dissolving the assemblies. Therefore, it was in force from 1962 to 1969. Options like 4, 5, or 6 years are incorrect as they do not accurately reflect the full duration of its operation. Its abrogation paved the way for the eventual framing of the 1973 Constitution.