Explanation:

All codes are correct.
The concept of 'basic structure' came into existence in the landmark judgment in Kesavananda Bharati case (1973). 
The 'basic structure' doctrine has been interpreted to include:

• the supremacy of the Constitution,  
• the rule of law,  
• Independence of the judiciary,
• doctrine of separation of powers, 
• sovereign, democratic, republic,
• Secular character of the Constitution, 
• Unity and Integrity of the nation o the parliamentary system of government, 
• Limited power of Parliament to amend the Constitution
• the principle of free and fair elections, 
• Judicial Review
• Welfare state, etc.

Hence option 4th is correct.