Detailed Explanation:

Answer: Option 3 — All State Government employees joining the services after the date of notification by the respective State Governments

✅ Option 3 – Correct: The National Pension System (NPS) was introduced by the Central Government on January 1, 2004. Subsequently, various State Governments adopted the NPS architecture for their employees. State Government employees joining after the date of notification by their respective State Governments are mandatorily covered under NPS.

❌ Option 1 – Incorrect: NPS is available to all Indian citizens including both Resident Indians and Non-Resident Indians (NRIs), not just resident Indian citizens.

❌ Option 2 – Incorrect: The eligibility age for joining NPS is 18 to 70 years, not 21 to 55 years. The age range was expanded over time to include a broader segment of citizens.

❌ Option 4 – Incorrect: NPS specifically excludes Armed Forces personnel. Additionally, the correct implementation date for Central Government employees was January 1, 2004, not April 1, 2004.